filter实现过滤压缩指定的请求的操作

filter过滤器的创建
package filter;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.zip.GZIPOutputStream;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

public class GzipFilter implements Filter {
// 这是一个用来将响应出去的数据进行压缩的处理过滤的类

@Override
public void destroy() {
// TODO Auto-generated method stub
}

@Override
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;

System.out.println("doFilter被执行在创建增强器MyRresponse之前.................");

// 对response响应的对象进行增强
MyRresponse myRresponse=new MyRresponse(response);
//执行目标方法带着增强后的对象
chain.doFilter(request, myRresponse);

//获取response对象中的流的原大小
byte resouceByte[]=myRresponse.getBuffer();

System.out.println("这是原数据的大小==========="+resouceByte.length);

//这是压缩之后的数据对象
ByteArrayOutputStream out=new ByteArrayOutputStream();
//创建压缩的流对象,接收字节输出流
GZIPOutputStream gzipOutputStream=new GZIPOutputStream(out);

//压缩流对象,并将数据写入压缩输出流对象
gzipOutputStream.write(resouceByte);
//关闭数据流
gzipOutputStream.close();

//得到压缩后的数据
byte gzipByte[]=out.toByteArray();

System.out.println("这是压缩后的数据大小==========="+gzipByte.length);

//高速浏览器以什么样的方式进行解析
//内容的编码方式
response.setHeader("Content-Encoding", "gzip");
//内容大小
response.setContentLength(gzipByte.length);
//将内容写入
response.getOutputStream().write(gzipByte);
}

@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}

// 这是对服务器输出流的增强
class MyServletOutputStream extends ServletOutputStream {

// 定义字节的输出流对象
private ByteArrayOutputStream baos;

public MyServletOutputStream(ByteArrayOutputStream baos) {
super();
this.baos = baos;
}

// 重写输输出流方法
@Override
public void write(int b) throws IOException {
// TODO Auto-generated method stub
baos.write(b);
}

}

// 这是对响应的数据进行增强的类
// 1.首先看需要被增强对象继承了什么接口或父类，编写一个类也去继承这些接口或父类
class MyRresponse extends HttpServletResponseWrapper {
// 缓冲区输出流的定义
private ByteArrayOutputStream baos = new ByteArrayOutputStream();

// 2.在类中定义一个变量,变量类型即需要增强对象的类型
private HttpServletResponse response;

// 创建文本输出流
private PrintWriter pw;

// 3.在类中定义一个构造函数，接收需增强的对象
public MyRresponse(HttpServletResponse response) {
super(response);
this.response = response;
}

// 4.覆盖被增强的方法,编写增强的功能
@Override
public ServletOutputStream getOutputStream() throws IOException {
return new MyServletOutputStream(baos);
}

@Override
public PrintWriter getWriter() throws IOException {
pw = new PrintWriter(new OutputStreamWriter(baos, "UTF-8"));
return pw;
}

// 自定义方法
public byte[] getBuffer() {
if (pw != null) {// 判断缓冲区是否写入数据
pw.close();
}
return baos.toByteArray();

}

}

}

web.xml文件的配置处理
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>jqueryeasyui</display-name>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>servlet.LoginServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login.do</url-pattern>
</servlet-mapping>

<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>filter.EncodingFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<filter>
<filter-name>GzipFilter</filter-name>
<filter-class>filter.GzipFilter</filter-class>
</filter>
<!-- 过滤指定的后缀请求-->
<filter-mapping>
<filter-name>GzipFilter</filter-name>
<url-pattern>*.jpg</url-pattern>
</filter-mapping>

<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>