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动态代理练习1-全站字符编码过滤[request动态代理]

2013-05-01 16:36 429 查看
1、全站字符编码过滤[request动态代理]

　　a)使用装饰设计模式

　　b)使用动态代理





开发步骤：

1)写一个普通类，无需任何继承或实现
2)写一个实例变量，记住代理谁，即目标对象
3)使用构造方法为实例变量赋值
4)写一个普通方法，该方法的返回值是接口，该接口是目标对象的实现接口

a)普通类-即代理类

import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//    过滤器
public class EncodingFilter implements Filter {

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

HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
MyRequest myRequest = new MyRequest(request);
chain.doFilter(myRequest.getProxy(),response);
}
public void init(FilterConfig filterConfig) throws ServletException {
}
public void destroy() {
}
}
//使用动态代理方式产生代理对象
class MyRequest{ //1、写一个普通类，无需任何继承或实现
private HttpServletRequest request;//2、代理谁，代理HttpServletRequest，写一个实例变量，记住代理谁，即目标对象
public MyRequest(HttpServletRequest request){//3、使用构造方法为实例变量赋值
this.request = request;
}
public HttpServletRequest getProxy(){//4、写一个普通方法，该方法的返回值是接口，该接口是目标对象的实现接口，即HttpServletRequest
return (HttpServletRequest) Proxy.newProxyInstance(
MyRequest.class.getClassLoader(),
request.getClass().getInterfaces(),
new InvocationHandler(){
public Object invoke(
Object proxy,
Method method,
Object[] args) throws Throwable {
if("getParameter".equals(method.getName())){
//取得请求的类型[POST或GET]
String m = request.getMethod();
//如果是GET请求类型
if("get".equalsIgnoreCase(m)){
String value = request.getParameter((String)args[0]);//乱码
byte[] buf = value.getBytes("ISO8859-1");
value = new String(buf,"UTF-8");//正码
return value;
}else if("post".equalsIgnoreCase(m)){
request.setCharacterEncoding("UTF-8");
String value = request.getParameter((String)args[0]);//正码
return value;
}
}else{
//放行
return method.invoke(request,args);
}
return null;
}
});
}
}


　　b)Servlet-即被代理的类

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class GetPostSetvlet extends HttpServlet {

public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
request.setCharacterEncoding("utf-8");
String method = request.getMethod();
String username = request.getParameter("username");
System.out.println("用户名["+method+"]:"+username);

}
public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
this.doGet(request, response);
}
}


　　c)jsp页面

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
<form action="${pageContext.request.contextPath}/GetPostSetvlet"  method="post">
<input type="text"  name="username"/>
<input type="submit"  value="登录"/>
</form>
</body>
</html>


　　d)web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>cn.zengfanshegn.proxy.servlet.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<servlet-name>GetPostSetvlet</servlet-name>
</filter-mapping>

<servlet>
<servlet-name>GetPostSetvlet</servlet-name>
<servlet-class>cn.zengfanshegn.proxy.servlet.GetPostSetvlet</servlet-class>
</servlet>
　　<servlet-mapping>
<servlet-name>GetPostSetvlet</servlet-name>
<url-pattern>/GetPostSetvlet</url-pattern>
</servlet-mapping>
</web-app>
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