Servlet中提供了4個包裝器類：可以改變Servlet請求和Servlet響應的行爲
允許將任何方法都包裝到ServletRequest和ServletResponse或HttpServletRequest和HttpServletRespnse中
使用：
編寫HttpServletRequestWrapper的子類
重寫getParameter等希望修改其行爲的方法
一般用於過濾器中
示例：
Filter.java
package com.ls.javaee;
import java.io.IOException;
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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
@WebFilter("*")
public class Filter1 implements Filter {
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
//String content=req.getParameter("content");
chain.doFilter(new MyWrapper((HttpServletRequest)req), res);
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}Servlet.java
package com.ls.javaee;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
public class MyWrapper extends HttpServletRequestWrapper {
private HttpServletRequest request;
public MyWrapper(HttpServletRequest request) {
super(request);
this.request = request;
}
@Override
public String getParameter(String name) {
String value=request.getParameter(name);
return value.replaceAll("1", "one");
}
}
Servlet1.java
package com.ls.javaee;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/test1")
public class Servlet1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println(request.getParameter("content"));
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the POST method");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}