Java HttpServletResponse

package ServletPackage;

import java.io.*;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletDemo1 extends HttpServlet {

    int i=1;
    private static final long serialVersionUID = 4312868947607181532L;

    /**
     * The doGet method of the servlet. 

     *
     * This method is called when a form has its tag value method equals to get.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

       //threadSafety(response);
        //outputHello(response);
       //outputChineseByPrintWriter(response);
        downloadFileByOutputStream(response);

    }

    /**
     * 下载文件
     */
    public void downloadFileByOutputStream(HttpServletResponse response) throws FileNotFoundException, IOException{
        //1.获取要下载文件的绝对路径
        String realPath = this.getServletContext().getRealPath("/img/timg.jpg");
        //2.获得要下载的文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\")+1);
        //3.设置Content-disposition响应头控制浏览器以下载的形式打开文件,中文文件名要使用URLEncoder.encode方法进行编码，否则会出现文件名乱码
        response.setHeader("content-disposition", "attachment;filename="+fileName);
        //response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(fileName, "UTF-8"));
        //4.获取要下载的文件输入流
        InputStream in = new FileInputStream(realPath);
        int len = 0;
        //5.创建数据缓冲区
        byte[] buffer = new byte[1024];
        //6.通过response对象获取OutputStream流
        OutputStream out = response.getOutputStream();
        //7.将FileInputStream流写入到buffer缓冲区
        while ((len = in.read(buffer)) > 0) {
            //8.使用OutputStream将缓冲区的数据输出到客户端浏览器
            out.write(buffer, 0, len);
        }

        in.close();

    }

    /**
     * 使用PrintWriter流输出中文
     */
    public void outputChineseByPrintWriter(HttpServletResponse response) throws IOException{
        String data = "中国";

        //通过设置响应头控制浏览器以UTF-8的编码显示数据，如果不加这句话，那么浏览器显示的将是乱码
        //response.setHeader("content-type", "text/html;charset=UTF-8");

        response.setCharacterEncoding("UTF-8");//设置将字符以"UTF-8"编码输出到客户端浏览器
        PrintWriter out = response.getWriter(); //此必须在设置编码之后

        out.write("");//等同于setHeader设置
        out.write(data);

        //输出数字
       /* response.setHeader("content-type", "text/html;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();//获取PrintWriter输出流
        out.write("使用PrintWriter流输出数字1：");
        out.write(1+"");*/
    }

    /**
     * 使用OutputStream流输出中文
     */
    public void outputChineseByOutPutStream(HttpServletResponse response) throws IOException{
        String str = "中国";

        OutputStream outputStream = response.getOutputStream();
        response.setHeader("content-type", "text/html;charset=UTF-8");

        byte[] strByteArray = str.getBytes("UTF-8");
        outputStream.write(strByteArray);

        //输出数字
      /*  response.setHeader("content-type", "text/html;charset=UTF-8");
        OutputStream outputStream = response.getOutputStream();
        outputStream.write("使用OutputStream流输出数字1：".getBytes("UTF-8"));
        //outputStream.write(1);
        outputStream.write((1+"").getBytes());*/
    }

    /**
     * Thread safety test
     */
    public void threadSafety(HttpServletResponse response) throws IOException{
        response.setHeader("refresh","3;url='http://www.baidu.com'");
        response.getWriter().write("gacl");


        synchronized (this) {
            i++;
            try {
                Thread.sleep(1000 * 4);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            response.getWriter().write(i + "");
        }


    }

    /**
    * Fistlly Testing
    */
    public void outputHello(HttpServletResponse response) throws IOException{
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("");
        out.println("");
        out.println("  ");
        out.println("  ");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("  ");
        out.println("");
        out.flush();
        out.close();
    }

    /**
     * The doPost method of the servlet. 

     *
     * This method is called when a form has its tag value method equals to post.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("");
        out.println("");
        out.println("  ");
        out.println("  ");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the POST method");
        out.println("  ");
        out.println("");
        out.flush();
        out.close();
    }

}

参考：HttpServletResponse对象(一)

Request类

1. setAttribute()在Request域中存储数据
2. setCharacterEncoding()设置请求参数的编码方式,只对post请求有效
3. getMethod()获取请求类型
4. getParameter()获取指定请求参数值
5. getParameterNames()获取所有请求参数,返回一个Enumeration枚举类
6. getAttribute()获取域中存储的数据
7. getAttributeNames()获取域中所有数据,返回一个Enumeration枚举类
8. getContextPath()返回当前WEB项目相对路径
9. getCookies()获取所有Cookie,返回一个Cookie数组
10. getRequestDispatcher()获取转发器,参数路径以/打头,代表WebRoot(当前WEB项目根目录)
11. getSession()获取Session对象

Response类

1. setContentType()告知浏览器数据类型
2. setCharacterEncoding设置Response的编码方式
3. setHeader()设置消息头
4. setStatus()设置状态吗
5. addCookie()添加Cookie
6. sendRedirect()重定向
7. getOutputStream()获取通向浏览器的字节流(同一次请求处理中,字节流和字符流不能同时存在)
8. getWriter()获取通向浏览器的字符流(同一次请求处理中,字节流和字符流不能同时存在)