JavaWeb学习内容

时间：2021-03-06 23:24:37 阅读：69 评论：0 收藏：0 [点我收藏+]

javaWeb

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java web

1、基本概念

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| #### 3.2、发布网站 |
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| - 将自己写的网站，放到服务器（tomcat）中指定的web应该的文件夹（webapps）下，就可以访问了 |
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| - 网站结构 |
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| java | | -- webapps : tomcat服务器web目录 | | -- root | | -- baidu ：网站目录名 | | -- WEB-INF | | | | | | | | | | | | | | | | | | | | | | |
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| ## 4、HTTP |
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| 4.1、http是什么 |
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| 超文本传输协议（Hypertext Transfer Protocol，HTTP）是一个简单的请求-响应协议，它通常运行在TCP之上。 |
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| - 文本：html，字符串，~ |
| - 超文本：图片，音乐，视频，定位，地图。。。 |
| - 默认端口：80 |
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| https：安全的 |
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| - 默认端口：443 |
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| ### 4.2、两个时代 |
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| - http1.0 |
| - HTTP/1.0 :客户端可以与web服务器连接后，只能获得一个web资源，断开连接 |
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| - http2.0 |
| - HTTP/1.1：客户端可以与web服务器连接后，可以获得多个web资源 |
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| ### 4.3、http请求 |
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| - 客户端--发请求--服务器 |
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| 百度 |
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| html | | Request URL: https://www.baidu.com/ 请求地址 | | Request Method: GET get方法/post方法 | | Status Code: 200 OK 状态码：200 | | Remote(远程) Address: 14.215.177.38:443 | | Referrer Policy: no-referrer-when-downgrade | | |
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| java | | Accept: text/html; | | Accept-Encoding: gzip, deflate, br | | Accept-Language: zh-CN,zh;q=0.9 | | Cache-Control: max-age=0 | | Connection: keep-alive | | |
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| 1. #### 请求行 |
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| - 请求行中的请求方式：GET |
| - 请求方式：CET，POST |
| - get：请求能够携带的参数比较少，大小有限制，会在浏览器的URL地址栏显示数据内容，不安全，但是高效 |
| - post：请求能够携带的参数没有限制，大小没有限制，不会在浏览器的URL地址栏显示数据内容，安全，但是不高效 |
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| 2. ### 消息头 |
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| java | | Accept: 告诉浏览器，他所支持的数据类型 | | Accept-Encoding: 支持那种编码格式 GBK UTF-8 GB2312 | | Accept-Language:告诉浏览器它的语言环境 | | Cache-Control:缓存控制 | | Connection: 告诉浏览器，请求完成是断开连接还是保持连接 | | HOST：主机 | | |
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| ### 4.4、http响应 |
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| - 服务器--响应--客户端 |
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| 百度： |
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| java | | Cache-Control: private // 缓存控制 | | Connection: keep-alive // 连接：保持 | | Content-Encoding: gzip //编码类型 | | Content-Type: text/html;charset=utf-8 | | |
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| #### 1、响应体 |
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| java | | Accept: 告诉浏览器，他所支持的数据类型 | | Accept-Encoding: 支持那种编码格式 GBK UTF-8 GB2312 | | Accept-Language:告诉浏览器它的语言环境 | | Cache-Control:缓存控制 | | Connection: 告诉浏览器，请求完成是断开连接还是保持连接 | | HOST：主机 | | Refresh:高数客户端，多久刷新一次 | | Location：让网页重新定位 | | |
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| #### 2、响应状态码 |
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| 200：请求响应成功 |
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| 3**：请求重定向 |
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| - 重定向：重新到新的位置去 |
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| 404：找不到资源 |
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| - 资源不存在 |
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| 5XX：服务器代码错误 500 |
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| 502：网关错误 |
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| 常见面试题： |
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| 当你的浏览器中地址栏输入地址并回车的一瞬间并能够展示回来，经历了什么？ |
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| ## 5、Maven |
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| ## 6、Servlet |
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| ### 6.1、Servlet简介 |
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| - Servlet就是sun公司开发动态web的一门技术 |
| - sun在这些API中提供一个接口叫做：servlet如果想开发一个servlet程序，只需要 |
| - 编写一个类，实现servlet接口 |
| - 把开发好的javalei部署到web服务器中 |
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| 把实现了servlet接口程序叫做，servlet |
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| ### 6.2、helloservlet |
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| Servlet接口在sun公司有两个默认实现类，HttpServlet，GenericServlet |
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| 1. 构件一个Maven项目，删掉类名的src目录，以后我们的学习就在这个项目里面建立项目，这个空的工程就是maven的主工程 |
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| 2. 关于maven父子工程的理解： |
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| 父项目会有 |
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| java | | <modules> | | <module>servlet-01</module> | | </modules> | | |
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| 子项目会有 |
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| java | | <parent> | | <artifactId>javaweb-02-servlet</artifactId> | | <groupId>com.bing</groupId> | | <version>1.0-SNAPSHOT</version> | | </parent> | | |
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| 3. Maven环境优化 |
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| 1. 修改web.xml |
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| java | | <?xml version="1.0" encoding="UTF-8"?> | | <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" | | xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" | | xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee | | http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" | | version="4.0" | | metadata-complete="true"> | | | | </web-app> | | | | |
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| 2. 将maven的结构搭建 |
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| 4. 编写一个Servlet程序 |
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| 1. 编写一个普通类 |
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| 2. 实现Servlet接口类，这里我们直接继承HttpServlet |
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| java | | public class HelloServlet extends HttpServlet { | | | | //由于get或者post只是请求实现的不同方式，可以相互调用，业务逻辑都一样 | | | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | | | PrintWriter writer = resp.getWriter(); //响应溜 | | | | writer.print("Hello Servlet"); | | } | | | | @Override | | protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | super.doPost(req, resp); | | } | | } | | |
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| 5. 编写Servlet的映射 |
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| 为什么需要映射：我们写的是java程序，但是要通过浏览器访问，而浏览器需要连接web服务器，所以我们需要再web服务器中注册我们写的Servlet，还需要给他一个浏览器能够找到的路径 |
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| java | | <servlet> | | <servlet-name>hello</servlet-name> | | <servlet-class>com.peng.servlet.HelloServlet</servlet-class> | | </servlet> | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello</url-pattern> | | </servlet-mapping> | | |
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| 6.配置Tomca |
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| ? |
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| 7.启动测试 OK！ |
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| ### 6.3 Servlet原理 |
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| 技术分享图片

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| ### 6.4、mapping问题 |
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| 1. 一个Servlet请求可以指定一个映射路径 |
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| | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello</url-pattern> | | </servlet-mapping> | | |
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| 2. 一个Servlet请求可以指定多个映射路径 |
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| java | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello</url-pattern> | | </servlet-mapping> | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello1</url-pattern> | | </servlet-mapping> | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello2</url-pattern> | | </servlet-mapping> | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello3</url-pattern> | | </servlet-mapping> | | |
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| 3. 一个Servlet请求可以指定通用个映射路径 |
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| java | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello/*</url-pattern> | | </servlet-mapping> | | |
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| 4.默认请求路径 |
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| java | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/*</url-pattern> | | </servlet-mapping> | | |
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| 5.优先级问题 |
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| ? |
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| ### 6.5、getServletContext |
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| #### 1、共享数据 |
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| web容器在启动的时候，它会为每个web程序都创建以对应的servletcontext对象，它代表了当前的web应用： |
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| - 共享数据 |
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| - 我在这个servlet中保存的数据，可以在另一个servlet对象中找到 |
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| java | | public class HelloServlet extends HttpServlet { | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | | | // this.getInitParameter(); 初始化参数 | | // this.getServletConfig(); Servlet配置 | | // this.getServletContext(); servlet上下文 | | ServletContext servletContext = this.getServletContext(); | | | | String username = "北五"; | | | | servletContext.setAttribute("username",username); //将一个数据保存在了ServletContext中，名字为username 指为username | | | | | | System.out.println("hello"); | | } | | } | | |
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| java | | public class Getservlet extends HttpServlet { | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | ServletContext context = this.getServletContext(); | | | | String username = (String) context.getAttribute("username"); | | | | resp.setContentType("text/html"); | | resp.setCharacterEncoding("UTF-8"); | | resp.getWriter().print("名字 :"+username); | | } | | | | @Override | | protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | doGet(req, resp); | | } | | } | | | | |
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| xml | | <servlet> | | <servlet-name>hello</servlet-name> | | <servlet-class>com.peng.servlet.HelloServlet</servlet-class> | | | | </servlet> | | <servlet-mapping> | | <servlet-name>hello</servlet-name> | | <url-pattern>/hello</url-pattern> | | </servlet-mapping> | | <servlet> | | <servlet-name>getc</servlet-name> | | <servlet-class>com.peng.servlet.Getservlet</servlet-class> | | </servlet> | | <servlet-mapping> | | <servlet-name>getc</servlet-name> | | <url-pattern>/getc</url-pattern> | | </servlet-mapping> | | | | |
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| 测试结果 |
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| #### 2、获取初始化参数 |
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| xml | |  | | <context-param> | | <param-name>url</param-name> | | <param-value>jdbc:mysql://localhost:3306/mybatis</param-value> | | </context-param> | | |
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| java | | public class ServletDemo03 extends HttpServlet { | | | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | ServletContext servletContext = this.getServletContext(); | | | | String url = servletContext.getInitParameter("url"); | | | | resp.getWriter().print(url); | | } | | | | @Override | | protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | doGet(req, resp); | | } | | } | | | | |
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| #### 3、请求转发 |
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| java | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | ServletContext context = this.getServletContext(); | | | | // RequestDispatcher requestDispatcher; | | // requestDispatcher = context.getRequestDispatcher("/Demo"); | | // requestDispatcher.forward(req, resp); //调用forward实现请求转发 | | | | context.getRequestDispatcher("/Demo3").forward(req, resp); | | |
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| 技术分享图片 |
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| #### 4、读取资源文件 |
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| Properties |
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| - 在java目录下新建properties |
| - 在ersources目录下新建properties |
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| 发现：都被打包到了一个同一个路径下：classes，这个路径我们俗称classpath |
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| 思路：需要一个文件流； |
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| properties | | username=beiwu | | password=123456 | | |
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| java | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties"); | | | | Properties properties = new Properties(); | | properties.load(is); | | String user = properties.getProperty("username"); | | String password = properties.getProperty("password"); | | | | resp.getWriter().print(user + ":" + password); | | } | | | | |
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| 访问测试OK！ |
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| ### 6.6、HttpServletResponse |
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| web服务器接收到客户端的http请求，针对这个请求，分别创建一个代表请求HttpServletRequest对象，代表响应的一个HttpServletResponse对象： |
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| - 如果要获取客户端请求过来的参数：找HttpServletRequest |
| - 如歌要给客户响应一些信息：找HttpServletResponse |
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| ### 1、简单分类 |
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| 负责向浏览器发送数据的方法： |
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| java | | public ServletOutputStream getOutputStream() throws IOException; | | public PrintWriter getWriter() throws IOException; | | |
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| 负责向浏览器发送一些响应头 |
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| java | | public void setCharacterEncoding(String charset); | | public void setContentLength(int len); | | public void setContentLengthLong(long len); | | public void setContentType(String type); | | public void setDateHeader(String name, long date); | | public void addDateHeader(String name, long date); | | public void setHeader(String name, String value); | | public void addHeader(String name, String value); | | public void setIntHeader(String name, int value); | | public void addIntHeader(String name, int value); | | |
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| 响应状态码 |
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| java | | /** | | * Status code (100) indicating the client can continue. | | */ | | public static final int SC_CONTINUE = 100; | | | | /** | | * Status code (101) indicating the server is switching protocols | | * according to Upgrade header. | | */ | | public static final int SC_SWITCHING_PROTOCOLS = 101; | | | | /** | | * Status code (200) indicating the request succeeded normally. | | */ | | public static final int SC_OK = 200; | | | | /** | | * Status code (201) indicating the request succeeded and created | | * a new resource on the server. | | */ | | public static final int SC_CREATED = 201; | | | | /** | | * Status code (202) indicating that a request was accepted for | | * processing, but was not completed. | | */ | | public static final int SC_ACCEPTED = 202; | | | | /** | | * Status code (203) indicating that the meta information presented | | * by the client did not originate from the server. | | */ | | public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203; | | | | /** | | * Status code (204) indicating that the request succeeded but that | | * there was no new information to return. | | */ | | public static final int SC_NO_CONTENT = 204; | | | | /** | | * Status code (205) indicating that the agent <em>SHOULD</em> reset | | * the document view which caused the request to be sent. | | */ | | public static final int SC_RESET_CONTENT = 205; | | | | /** | | * Status code (206) indicating that the server has fulfilled | | * the partial GET request for the resource. | | */ | | public static final int SC_PARTIAL_CONTENT = 206; | | | | /** | | * Status code (300) indicating that the requested resource | | * corresponds to any one of a set of representations, each with | | * its own specific location. | | */ | | public static final int SC_MULTIPLE_CHOICES = 300; | | | | /** | | * Status code (301) indicating that the resource has permanently | | * moved to a new location, and that future references should use a | | * new URI with their requests. | | */ | | public static final int SC_MOVED_PERMANENTLY = 301; | | | | /** | | * Status code (302) indicating that the resource has temporarily | | * moved to another location, but that future references should | | * still use the original URI to access the resource. | | * | | * This definition is being retained for backwards compatibility. | | * SC_FOUND is now the preferred definition. | | */ | | public static final int SC_MOVED_TEMPORARILY = 302; | | | | /** | | * Status code (302) indicating that the resource reside | | * temporarily under a different URI. Since the redirection might | | * be altered on occasion, the client should continue to use the | | * Request-URI for future requests.(HTTP/1.1) To represent the | | * status code (302), it is recommended to use this variable. | | */ | | public static final int SC_FOUND = 302; | | | | /** | | * Status code (303) indicating that the response to the request | | * can be found under a different URI. | | */ | | public static final int SC_SEE_OTHER = 303; | | | | /** | | * Status code (304) indicating that a conditional GET operation | | * found that the resource was available and not modified. | | */ | | public static final int SC_NOT_MODIFIED = 304; | | | | /** | | * Status code (305) indicating that the requested resource | | * <em>MUST</em> be accessed through the proxy given by the | | * <code><em>Location</em></code> field. | | */ | | public static final int SC_USE_PROXY = 305; | | | | /** | | * Status code (307) indicating that the requested resource | | * resides temporarily under a different URI. The temporary URI | | * <em>SHOULD</em> be given by the <code><em>Location</em></code> | | * field in the response. | | */ | | public static final int SC_TEMPORARY_REDIRECT = 307; | | | | /** | | * Status code (400) indicating the request sent by the client was | | * syntactically incorrect. | | */ | | public static final int SC_BAD_REQUEST = 400; | | | | /** | | * Status code (401) indicating that the request requires HTTP | | * authentication. | | */ | | public static final int SC_UNAUTHORIZED = 401; | | | | /** | | * Status code (402) reserved for future use. | | */ | | public static final int SC_PAYMENT_REQUIRED = 402; | | | | /** | | * Status code (403) indicating the server understood the request | | * but refused to fulfill it. | | */ | | public static final int SC_FORBIDDEN = 403; | | | | /** | | * Status code (404) indicating that the requested resource is not | | * available. | | */ | | public static final int SC_NOT_FOUND = 404; | | | | /** | | * Status code (405) indicating that the method specified in the | | * <code><em>Request-Line</em></code> is not allowed for the resource | | * identified by the <code><em>Request-URI</em></code>. | | */ | | public static final int SC_METHOD_NOT_ALLOWED = 405; | | | | /** | | * Status code (406) indicating that the resource identified by the | | * request is only capable of generating response entities which have | | * content characteristics not acceptable according to the accept | | * headers sent in the request. | | */ | | public static final int SC_NOT_ACCEPTABLE = 406; | | | | /** | | * Status code (407) indicating that the client <em>MUST</em> first | | * authenticate itself with the proxy. | | */ | | public static final int SC_PROXY_AUTHENTICATION_REQUIRED = 407; | | | | /** | | * Status code (408) indicating that the client did not produce a | | * request within the time that the server was prepared to wait. | | */ | | public static final int SC_REQUEST_TIMEOUT = 408; | | | | /** | | * Status code (409) indicating that the request could not be | | * completed due to a conflict with the current state of the | | * resource. | | */ | | public static final int SC_CONFLICT = 409; | | | | /** | | * Status code (410) indicating that the resource is no longer | | * available at the server and no forwarding address is known. | | * This condition <em>SHOULD</em> be considered permanent. | | */ | | public static final int SC_GONE = 410; | | | | /** | | * Status code (411) indicating that the request cannot be handled | | * without a defined <code><em>Content-Length</em></code>. | | */ | | public static final int SC_LENGTH_REQUIRED = 411; | | | | /** | | * Status code (412) indicating that the precondition given in one | | * or more of the request-header fields evaluated to false when it | | * was tested on the server. | | */ | | public static final int SC_PRECONDITION_FAILED = 412; | | | | /** | | * Status code (413) indicating that the server is refusing to process | | * the request because the request entity is larger than the server is | | * willing or able to process. | | */ | | public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413; | | | | /** | | * Status code (414) indicating that the server is refusing to service | | * the request because the <code><em>Request-URI</em></code> is longer | | * than the server is willing to interpret. | | */ | | public static final int SC_REQUEST_URI_TOO_LONG = 414; | | | | /** | | * Status code (415) indicating that the server is refusing to service | | * the request because the entity of the request is in a format not | | * supported by the requested resource for the requested method. | | */ | | public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415; | | | | /** | | * Status code (416) indicating that the server cannot serve the | | * requested byte range. | | */ | | public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416; | | | | /** | | * Status code (417) indicating that the server could not meet the | | * expectation given in the Expect request header. | | */ | | public static final int SC_EXPECTATION_FAILED = 417; | | | | /** | | * Status code (500) indicating an error inside the HTTP server | | * which prevented it from fulfilling the request. | | */ | | public static final int SC_INTERNAL_SERVER_ERROR = 500; | | | | /** | | * Status code (501) indicating the HTTP server does not support | | * the functionality needed to fulfill the request. | | */ | | public static final int SC_NOT_IMPLEMENTED = 501; | | | | /** | | * Status code (502) indicating that the HTTP server received an | | * invalid response from a server it consulted when acting as a | | * proxy or gateway. | | */ | | public static final int SC_BAD_GATEWAY = 502; | | | | /** | | * Status code (503) indicating that the HTTP server is | | * temporarily overloaded, and unable to handle the request. | | */ | | public static final int SC_SERVICE_UNAVAILABLE = 503; | | | | /** | | * Status code (504) indicating that the server did not receive | | * a timely response from the upstream server while acting as | | * a gateway or proxy. | | */ | | public static final int SC_GATEWAY_TIMEOUT = 504; | | | | /** | | * Status code (505) indicating that the server does not support | | * or refuses to support the HTTP protocol version that was used | | * in the request message. | | */ | | public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505; | | |
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| 2、常见应用 |
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| 1.向浏览器输出信息 |
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| ### 2、下载文件 |
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| 1. 要获取下载文件的路径 |
| 2. 下载文件名是啥？ |
| 3. 设置想办法让浏览器能够支持我们需要的东西 |
| 4. 获取下载文件的输入流 |
| 5. 创建缓冲区 |
| 6. 通过获得OutputStream对象 |
| 7. 将FileOutputStream流写入到buffer缓冲区 |
| 8. 使用OutputStream将缓冲区中的数据输出到客户端 |
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| java | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | // 1. 要获取下载文件的路径 | | String path = "E:\\java\\web\\javaweb-01-servlet\\response\\target\\response\\WEB-INF\\classes\\1.png"; | | System.out.println("下载文件的路径：" + path); | | // 2. 下载文件名是啥？ | | String fileName = path.substring(path.lastIndexOf("\\") + 1); | | | | // 3. 设置想办法让浏览器能够支持我们需要的东西 | | resp.setHeader("Content-Disposition","attachment;filename="+fileName); | | // 4. 获取下载文件的输入流 | | FileInputStream in = new FileInputStream(path); | | // 5. 创建缓冲区 | | int len = 0; | | byte[] buffer = new byte[1024]; | | // 6. 通过获得OutputStream对象 | | ServletOutputStream outputStream = resp.getOutputStream(); | | // 7. 将FileOutputStream流写入到buffer缓冲区 | | while ((len=in.read(buffer))>0){ | | outputStream.write(buffer,0,len); | | } | | in.close(); | | outputStream.close(); | | // 8. 使用OutputStream将缓冲区中的数据输出到客户端 | | } | | |
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| ### 3、验证码功能 |
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| 验证码怎么来的？ |
| |
| - 前端实现 |
| - 后端实现，需要用到ava的图片类，生成一个图片 |
| |
| java | | public class ImageServlet extends HttpServlet { | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { | | //如何让浏览器5秒刷新一次 | | resp.setHeader("refresh", "5"); | | | | //在内存中创建图片 | | BufferedImage image = new BufferedImage(65, 22, BufferedImage.TYPE_INT_RGB); | | //等到图片 | | Graphics2D graphics = (Graphics2D) image.getGraphics();//?? | | //设置图片的背景颜色 | | graphics.setColor(Color.YELLOW); | | graphics.fillRect(0, 0, 65, 22); | | | | //给图片写数据 | | graphics.setColor(Color.BLUE); | | graphics.setFont(new Font(null, Font.BOLD, 20)); | | graphics.drawString(makeNum(), 0, 22); | | | | //告诉浏览器用图片的方式打开 | | resp.setContentType("image/jpeg"); | | | | //网站存在缓存，不让浏览器缓存 | | resp.setDateHeader("expires", -1); | | resp.setHeader("Cache-Control", "no-cache"); | | resp.setHeader("Pragma", "no-cache"); | | | | //把图片写给浏览器 | | // ImageIO.write(image, "jpg", resp.getOutputStream()); | | JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(resp.getOutputStream()); | | encoder.encode(image); | | | | } | | | | //生成随机数 | | private String makeNum() { | | Random random = new Random(); | | String num = random.nextInt(999999) + ""; | | StringBuffer buffer = new StringBuffer(); | | for (int i = 0; i < 6 - num.length(); i++) { | | buffer.append("0"); | | } | | num = buffer.toString() + num; | | return num; | | } | | | | | | @Override | | protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | doGet(req, resp); | | } | | } | | | | |
| |
| |
| |
| ### 4、重定向 |
| |
| |
| |
| >java | | >public void sendRedirect(String location) throws IOException; | | > |
| |
| java | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | | | | | // resp.setHeader("Location","/i/img"); | | // resp.setStatus(302); | | resp.sendRedirect("/i/img"); //重定向 | | } | | |
| |
| 面试题：请你聊聊重定向和转发的区别 |
| |
| 相同点 |
| |
| - 页面都会实现跳转 |
| |
| 不同点 |
| |
| - 请求转发的时候URL不会产生变化 307 |
| - 重定向的时候URL地址栏会发生变化； 302 |
| |
| 技术分享图片

| |
| |
| |
| |
| |
| jsp | | <html> | | <body> | | <h2>Hello World!</h2> | | | | <%--这里提交的路径，需要寻找到项目的路径--%> | | <%--${pageContext.request.contextPath}代表当前项目--%> | | <form action="${pageContext.request.contextPath}/login" method="get"> | | 用户名：<input type="text" name="username"> <br> | | 密码：<input type="password" name="password"> <br> | | <input type="submit"> | | </form> | | | | </body> | | </html> | | | | |
| |
| java | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | //处理请求 | | String username = req.getParameter("username"); | | String password = req.getParameter("password"); | | | | System.out.println(username + ":" + password); | | resp.sendRedirect("/i/success.jsp"); | | } | | |
| |
| ### 6.7、HttpServletRequest |
| |
| HttpServletRequest代表客户端的请求，用户通过HTTP协议访问服务器，HTTP请求种的所有信息都被封装到HttpServletRequest，通过这个HttpServletRequest的方法可以获得客户端的所有信息 |
| |
| 1、获取前端传递的参数 |
| |
| 2、请求转发 |
| |
| jsp | | <%-- | | Created by IntelliJ IDEA. | | User: 79925 | | Date: 2021/3/1 | | Time: 21:17 | | To change this template use File | Settings | File Templates. | | --%> | | <%@ page contentType="text/html;charset=UTF-8" language="java" %> | | <html> | | <head> | | <title>登录</title> | | </head> | | <body> | | <h1>登录</h1> | | | | <div style="text-align: center"> | | <form action="${pageContext.request.contextPath}/login" method="post"> | | 用户名：<input type="text" name="username"> <br> | | 密码：<input type="password" name="password"><br> | | 爱好： | | <input type="checkbox" name="hobby" value="女孩">女孩 | | <input type="checkbox" name="hobby" value="代码">代码 | | <input type="checkbox" name="hobby" value="唱歌">唱歌 | | <input type="checkbox" name="hobby" value="电影">电影 | | <br> | | <input type="submit"> | | </form> | | | | </div> | | </body> | | </html> | | | | |
| |
| java | | public class LoginServlet extends HttpServlet { | | @Override | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | req.setCharacterEncoding("utf-8"); | | resp.setCharacterEncoding("utf-8"); | | String username = req.getParameter("username"); | | String password = req.getParameter("password"); | | String[] hobbies = req.getParameterValues("hobby"); | | | | System.out.println("========================="); | | System.out.println(username); | | System.out.println(password); | | System.out.println(Arrays.toString(hobbies)); | | | | // | | // resp.sendRedirect("/r/success.jsp"); | | | | req.getRequestDispatcher(" /success.jsp").forward(req, resp); | | | | } | | } | | | | |
| |
| |
| |
| ## 7、Cookie、Session |
| |
| ### 7.1、会话 |
| |
| 会话：用户打开一个浏览器，点击了很多超链接，访问多个web资源，关闭浏览器，这个过程可以称之为会话 |
| |
| 有状态的会话： |
| 一个网站，怎么证明你来过？ |
| |
| 客户端服务端 |
| |
| 1、服务端给客户端一个信件，客户端下次访问服务端带上信件就可以了cooick |
| |
| 2、服务器登记你来过，下次你来的时候我来匹配你 seesion |
| |
| |
| |
| ### 7.2、保持会话的两种技术 |
| |
| cookoe |
| |
| - 客户端技术（请求，响应） |
| |
| session |
| |
| - 服务器技术，利用这个技术，可以保持用户的会话信息，我们可以把信息或者数据放在session中 |
| |
| 常见：网站登录之后，第二次访问就无需登录 |
| |
| ### 7.3、cookie |
| |
| 1.从请求中拿到cookie信息 |
| |
| 2.服务端响应给客户端cookie |
| |
| java | | Cookie[] cookies = req.getCookies();//返回数组，说明cookie可能有多个 | | cookie.getName();//获取cookie中的key | | cookie.getValue()：//获取cookie中的value | | Cookie cookie = new Cookie("name", System.currentTimeMillis() + "");//新建一个cookie | | cookie.setMaxAge(20*60*60);//设置cookie有效期 | | resp.addCookie(cookie);//响应给客户端 | | |
| |
| cookie：一般会保存在本地文件 |
| |
| 一个网站cookie存在上线 |
| |
| - 一个cookie只能保存一个信息 |
| - 一个web站点可以给浏览器发送多个cookie，最多存放20个cookie |
| - cookie大小有限制4kb |
| - 300个cookie浏览器上线 |
| |
| 删除cookie |
| |
| - 不设置有效期，关闭浏览器，自动失效 |
| |
| java | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | //服务器告诉你来的时间，把这个信件带着，我就知道是你来了 | | | | //解决中文乱码 | | req.setCharacterEncoding("utf-8"); | | resp.setCharacterEncoding("utf-8"); | | PrintWriter out = resp.getWriter(); | | //Cookie ，服务端从客户端获取 | | Cookie[] cookies = req.getCookies();//返回数组，说明cookie可能有多个 | | | | //判断cookie是否存在 | | if (cookies != null) { | | //如果存在怎么办 | | out.write("上一次访问的时间"); | | for (int i = 0; i < cookies.length; i++) { | | Cookie cookie = cookies[i]; | | if (cookie.getName().equals("name")) { | | //获取cookie中的值 | | long aLong = Long.parseLong(cookie.getValue()); | | Date date = new Date(aLong); | | out.write(date.toLocaleString()); | | } | | } | | } else { | | out.write("这是您第一次访问"); | | } | | | | //服务器给客户端响应一个cookie | | Cookie cookie = new Cookie("name", System.currentTimeMillis() + ""); | | | | cookie.setMaxAge(20*60*60);//设置cookie有效期 | | resp.addCookie(cookie);//响应给客户端 | | | | } | | | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | //服务器告诉你来的时间，把这个信件带着，我就知道是你来了 | | | | //服务器给客户端响应一个cookie | | Cookie cookie = new Cookie("name", System.currentTimeMillis() + ""); | | | | cookie.setMaxAge(0);//设置cookie有效期 | | resp.addCookie(cookie);//响应给客户端 | | | | } | | | | | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | | | //解决中文乱码 | | req.setCharacterEncoding("utf-8"); | | resp.setCharacterEncoding("utf-8"); | | PrintWriter out = resp.getWriter(); | | Cookie[] cookies = req.getCookies(); | | if (cookies != null) { | | out.write("你上次访问的名称是："); | | for (int i = 0; i < cookies.length; i++) { | | Cookie cookie = cookies[i]; | | if (cookie.getName().equals("name")) { | | System.out.println(cookie.getValue()); | | out.write(cookie.getValue()); | | } | | | | } | | } else { | | out.write("这是你第一次访问！"); | | } | | Cookie cookie = new Cookie("name", "北五"); | | | | resp.addCookie(cookie); | | | | } | | | | |
| |
| |
| |
| ### 7.4、Session |
| |
| 什么是sessio： |
| |
| - 服务器会给用户（浏览器）创建一个session对象 |
| - 一个session独占一个浏览器，只要浏览器没有关闭，这个session就存在 |
| - 用户登录之后，整个网站他都可以访问！-->保存用户信息，保存购物车信息 |
| |
| Session和Cookie的区别： |
| |
| - Cookie是把用户的数据写给用户的浏览器，浏览器保存 |
| - Session把用户的数据写到用户独占Session中，服务端保存 |
| - Session对象由服务器创建； |
| |
| 使用场景： |
| |
| - 保存用户登录信息 |
| - 购物车信息 |
| - 在整个网站中经常会使用的数据，我们将他保存在Session中 |
| |
| 使用Sessio |
| |
| java | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | resp.setCharacterEncoding("utf-8"); | | req.setCharacterEncoding("utf-8"); | | resp.setContentType("text/html;charset=utf-8"); | | | | //等到session | | HttpSession session = req.getSession(); | | session.setAttribute("name", new Person("北五", 19)); | | | | String id = session.getId(); | | if (session.isNew()) { | | resp.getWriter().write("session创建成功，ID：" + id); | | } else { | | resp.getWriter().write("session已存在，ID：" + id); | | } | | | | | | protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | | resp.setCharacterEncoding("utf-8"); | | req.setCharacterEncoding("utf-8"); | | resp.setContentType("text/html;charset=utf-8"); | | | | //等到session | | HttpSession session = req.getSession(); | | Person name = (Person) session.getAttribute("name"); | | System.out.println(name); | | } | | | | HttpSession session = req.getSession(); | | session.removeAttribute("name"); // | | session.invalidate();//注销 | | |
| |
| 会话自动过期web.xml配置 |
| |
| xml | | <session-config> | |  | | <session-timeout>10</session-timeout> | | </session-config> | | |
| |
| ## 8、JSP |
| |
| ### 8.1、什么是JSP |
| |
| java Server Pages:java服务器端页面，也和Servlet一样，用于静态web技术 |
| |
| 最大的特点： |
| |
| - 写JSP就像在写HTML |
| - 区别： |
| - HTML只给用户提供静态的数据 |
| - JSP页面可以嵌套JAVA代码，为用户提供了动态服务 |
| |
| ### 8.2、JSP原理 |
| |
| 思路：JSP到底怎么执行的 |
| |
| |
| |
| ### 8.3、JSP基础语法 |
| |
| 任何语言都有自己的语法，JAVA有，JSP作为JAVA技术的一种应用，它拥有一些自己扩充的语法，Java所有的语法都支持 |
| |
| JSP表达式 |
| |
| java | | <%--JSP表达式 | | 作用：用来将程序的输出，输出到客户端 | | <%= 变量或者表达式%> | | --%> | | | | <%=new java.util.Date()%> | | |
| |
| JSP脚本片段 |
| |
| java | | <%--JSP表达式 | | 作用：用来将程序的输出，输出到客户端 | | <%= 变量或者表达式%> | | --%> | | | | <%=new java.util.Date()%> | | |
| |
| 脚本片段 |
| |
| jsp | | <% int x = 10; | | out.println(x); | | %> | | <p>这是一个JSP文档</p> | | <% | | | | int y = 2; | | out.println(y); | | %> | | | | <hr> | | | | <% | | for (int i = 0; i < 5; i++) { | | %> | | <h1>hello <%=i%> </h1> | | <% | | } | | %> | | |
| |
| JSP声明 |
| |
| >jsp | | ><%! | | > | | >static { | | > System.out.println("加载中。。。。"); | | >} | | > | | >private int globalvar = 0; | | > | | >public void c() { | | > System.out.println("c"); | | >} | | >%> | | > |
| > |
| >会被编译到JSP生成的Java的类中,其他的就会被生成到_jspService方法中! |
| |
| 在JSP中嵌入JAVA代码即可 |
| |
| ### 8.4、JSP指令 |
| |
| java | | %@include | | | | <%@include file="common/header.jsp" %> | | <h1>网页主体</h1> | | <%@include file="common/footer.jsp" %> | | | | <hr> | | | | <%--JSP标签--%> | | <jsp:include page="common/header.jsp"/> | | <h1>网页主体</h1> | | <jsp:include page="common/footer.jsp"/> | | | | |
| |
| ### 8.5、九大内置对象 |
| |
| - PageContext 存东西 |
| - Request 存东西 |
| - Respone |
| - Session 存东西 |
| - Application [SerlvetContext] 存东西 |
| - config [SerlvetConfig] |
| - out |
| - page |
| - exception |
| |
| java | | pageContext.setAttribute("name1", "1号"); //保存的数据只在一个页面中有效 | | request.setAttribute("name2", "2号"); //保存的数据只在一次请求中有效，请求转发会携带这个数据 | | session.setAttribute("name3", "3号"); //保存的数只在一次会话中有效，从浏览器打开到关闭 | | application.setAttribute("name4", "4号"); //保存的数据只在服务器中，从服务器到关闭 | | |
| |
| request:客户端向服务器发送请求,产生的数据,用户看完了就没用了,例如:看新闻 |
| |
| session:客户端向服务器发送请求,产生的数据,用户用完一会还有用,比如购物车 |
| |
| 8.6、JSP标签、JSTL标签、EL表达式 |
| |
| xml | |  | | <dependency> | | <groupId>taglibs</groupId> | | <artifactId>standard</artifactId> | | <version>1.1.2</version> | | </dependency> | |  | | <dependency> | | <groupId>javax.servlet.jsp.jstl</groupId> | | <artifactId>jstl</artifactId> | | <version>1.2</version> | | </dependency> | | |
| |
| EL表达式:${} |
| |
| - 获取数据 |
| - 执行运算 |
| - 获取web开方的常用对象 |
| |
| JSP标签 |
| |
| jsp | | <jsp:forward page="jsptag2.jsp"> | | <jsp:param name="value1" value="1"/> | | <jsp:param name="value2" value="2"/> | | </jsp:forward> | | | | | | 键：<%=request.getParameter("value1")%> | | 值：<%=request.getParameter("1")%> | | |
| |
| JSTL标签 |
| |
| JSTL标签库的使用就是为了弥补HTML标签的不足，它自定义了许多标签，可以供我们使用，标签的功能和java代码一样 |
| |
| jsp | | <body> | | | | <c:set value="89" var="score"/> | | <c:choose> | | <c:when test="${score>=90}"> | | 你的成绩优秀 | | </c:when> | | <c:when test="${score>=80}"> | | <c:out value="你的成绩良好"/> <br> | | </c:when> | | </c:choose> | | | | <% | | | | ArrayList<String> strings = new ArrayList<>(); | | | | strings.add(0, "张三"); | | strings.add(1, "李四"); | | strings.add(2, "王五"); | | strings.add(3, "赵六"); | | strings.add(4, "田七"); | | request.setAttribute("list", strings); | | %> | | <%-- | | var :每次遍历出来的变量 | | items：要遍历的对象 | | begin：从哪里开始 | | end：结束位置 | | step:步长 | | --%> | | <c:forEach var="strings" items="${list}"> | | <c:out value="${strings}"/> <br> | | </c:forEach> | | <hr> | | <c:forEach var="strings" items="${list}" begin="0" end="3" step="1"> | | <c:out value="${strings}"/> <br> | | </c:forEach> | | | | </body> | | |
| |
| |
| |
| 核心标签 |
| |
| 格式化标签 |
| |
| SQL标签 |
| |
| ## 9、JavaBean |
| |
| 实体类 |
| |
| JavaBean有特写的写法： |
| |
| - 必须要有一个无参构造 |
| - 属性必须私有化 |
| - 必须有对应的get/set方法 |
| |
| 一般用来和数据的字段做映射 ORM |
| |
| ORM：对象关系映射 |
| |
| - 表---->类 |
| - 字段---->属性 |
| - 行记录--->对象 |
| |
| | i | name | age | address | |
| | ---- | ---- | ---- | ------- | |
| | 1 | 北五 | 10 | 成都 | |
| | 2 | 行三 | 17 | 成都 | |
| | 3 | 一品 | 29 | 成都 | |
| |
| java | | class Peopel{ | | private int id; | | private String name; | | private int age; | | private String address; | | } | | | | class A{ | | new Peopel(1,"北五",10,"成都"); | | new Peopel(2,"行三",13,"成都"); | | | | } | | |
| |
| ## 10、MCV三层架构 |
| |
| 什么是MVC：Model view Controller 模型、视图、控制器 |
| |
| ### 10.1、早些年 |
| |
| 技术分享图片

- 登录验证

| |
| Filter步骤 |
| |
| 1. 导包 |
| |
| 2. java | | public class CharacterEncodingFilter implements Filter { | | | | //初始化 | | @Override | | public void init(FilterConfig filterConfig) throws ServletException { | | System.out.println("CharacterEncodingFilter初始化"); | | } | | | | // filterChain ：链 | | // 过滤器中的所有代码，再过来特定请求的时候会执行 | | // 必须 | | @Override | | public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { | | servletRequest.setCharacterEncoding("UTF-8"); | | servletResponse.setCharacterEncoding("UTF-8"); | | servletResponse.setContentType("text/html;charset=UTF-8"); | | | | | | System.out.println("CharacterEncodingFilter执行前。。。。"); | | filterChain.doFilter(servletRequest,servletResponse); //如果不写直接被拦截了，下面的不会被执行 | | System.out.println("CharacterEncodingFilter执行后。。。"); | | } | | //销毁 | | @Override | | public void destroy() { | | System.out.println("CharacterEncodingFilter销毁"); | | | | } | | } | | | | |
| |
| 3. 在web.xml中配置过滤器 |
| |
| 4. xml | | <servlet> | | <servlet-name>ShowServlet</servlet-name> | | <servlet-class>com.bin.servlet.ShowServlet</servlet-class> | | </servlet> | | <servlet-mapping> | | <servlet-name>ShowServlet</servlet-name> | | <url-pattern>/servlet/show</url-pattern> | | </servlet-mapping> | | <filter> | | <filter-name>CharacterEncodingFilter</filter-name> | | <filter-class>com.bin.filter.CharacterEncodingFilter</filter-class> | | </filter> | |  | | <filter-mapping> | | <filter-name>CharacterEncodingFilter</filter-name> | | <url-pattern>/servlet/*</url-pattern> | | </filter-mapping> | | |
| |
| ## 12、监听器 |
| |
| 实现一个监听器的接口 |
| |
| 1. 编写一个监听器 |
| |
| 2. 实现一个接口，重写方法 |
| |
| java | | //统计网站在线人数 | | public class OnlineCountListener implements HttpSessionListener { | | | | //创建session监听：看你的一举一动 | | //一旦创建session就会触发一次这个事件 | | @Override | | public void sessionCreated(HttpSessionEvent httpSessionEvent) { | | ServletContext context = httpSessionEvent.getSession().getServletContext(); | | Integer onlineCount = (Integer) context.getAttribute("OnlineCount"); | | | | if (onlineCount == null) { | | onlineCount = new Integer(1); | | } else { | | int count = onlineCount.intValue(); | | | | onlineCount = new Integer(count + 1); | | } | | | | context.setAttribute("OnlineCount", onlineCount); | | } | | | | @Override | | public void sessionDestroyed(HttpSessionEvent httpSessionEvent) { | | ServletContext context = httpSessionEvent.getSession().getServletContext(); | | Integer onlineCount = (Integer) context.getAttribute("OnlineCount" ); | | | | if (onlineCount == null) { | | onlineCount = new Integer(0); | | } else { | | int count = onlineCount.intValue(); | | | | onlineCount = new Integer(count - 1); | | } | | | | context.setAttribute("OnlineCount", onlineCount); | | } | | } | | |
| |
| 3. 配置web.xml |
| |
| xml | | <listener> | | <listener-class>com.bin.listener.OnlineCountListener</listener-class> | | </listener> | | |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| ## 13、JDBC |
| |
| java | | public static void main(String[] args) throws ClassNotFoundException, SQLException { | | | | | | //配置信息 | | //解决中文乱码useUnicode=true&characterEncoding=utf8 | | String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf8"; | | String username = "root"; | | String password = "123456"; | | //加载驱动 | | Class.forName("com.mysql.jdbc.Driver"); | | //连接数据库 | | Connection connection = DriverManager.getConnection(url, username, password); | | //向数据库发送SQL的对象Statement | | Statement statement = connection.createStatement(); | | | | //编写sql语句 | | String sql = "select * from users"; | | //执行查询sql | | ResultSet resultSet = statement.executeQuery(sql); | | | | while (resultSet.next()){ | | System.out.println("ID:"+resultSet.getObject("id")); | | System.out.println("name:"+resultSet.getObject("name")); | | System.out.println("password:"+resultSet.getObject("password")); | | System.out.println("email:"+resultSet.getObject("email")); | | System.out.println("birthday:"+resultSet.getObject("birthday")); | | } | | | | //关闭连接 | | resultSet.close(); | | statement.cancel(); | | connection.close(); | | | | | | | | } | | |
| |
| 导入Sql依赖 |
| |
| xml | | <dependency> | | <groupId>mysql</groupId> | | <artifactId>mysql-connector-java</artifactId> | | <version>5.1.49</version> | | </dependency> | | |
| |
| 连接数据库 |
| |
| 技术分享图片

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原文：https://www.cnblogs.com/huangwenpeng/p/14492094.html

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