我们就直接切入主题啦，文件下载只需要四步：
1.设置文件ContentType类型
2.设置文件头
3.通过response获取ServletOutputStream对象(out)
4.写到输出流(out)中
下载代码：
这里我使用的是SpringMVC，不过它在这里的唯一用途就是用来获取ServletContext对象，这个对象的用途，下面实例中有说明
下载，需要用到两个jar包：commons-fileupload.jar和commons-io.jar
- import org.springframework.stereotype.Controller;
- import org.springframework.web.bind.annotation.RequestMapping;
- import org.springframework.web.context.ServletContextAware;
-
- import javax.servlet.ServletContext;
- import javax.servlet.ServletOutputStream;
- import javax.servlet.http.HttpServletResponse;
- import java.io.*;
-
- @Controller
- public class FileController implements ServletContextAware{
-
- private ServletContext servletContext;
-
-
- @RequestMapping("file/download")
- public void fileDownload(HttpServletResponse response){
-
- String path = servletContext.getRealPath("/");
-
-
- response.setContentType("multipart/form-data");
-
- response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");
- ServletOutputStream out;
-
- File file = new File(path + "download/" + "download.pdf");
-
- try {
- FileInputStream inputStream = new FileInputStream(file);
-
-
- out = response.getOutputStream();
-
- int b = 0;
- byte[] buffer = new byte[512];
- while (b != -1){
- b = inputStream.read(buffer);
-
- out.write(buffer,0,b);
- }
- inputStream.close();
- out.close();
- out.flush();
-
- } catch (IOException e) {
- e.printStackTrace();
- }
- }
-
- @Override
- public void setServletContext(ServletContext servletContext) {
- this.servletContext = servletContext;
- }
- }
java文件下载
原文：http://www.cnblogs.com/liubaihui/p/7467173.html
