过滤器入门

	过滤器的概念及执行基本流程

	过滤器的使用场景

	过滤器的实现及基本配置

过滤器链

	过滤器链的配置

		使用注解的方式无法保证过滤器链的执行顺序，所以只能使用web.xml的配置

		按照出现在web.xml的filter-mapping顺序依次经过过滤器

异步过滤器

	与异步servlet类似

	异步过滤器的配置

	注解方式：设置@webfilter的属性asyncsupport属性为true

	web.xml方式：

与请求分派协作

	dispatcherTypes=DispatcherType.INCLUDE
	

包装器

	包装器的概念

	包装器类的使用

	在servlet api中提供了4个包装器类

	与装饰器的设计模式相类似

	允许将任何方法都包装到servletrequest...之中

	javax.servlet.ServletRequestWrapper，在其后加wrapper

一、servlet

package com.fgy;

import java.io.IOException;

import javax.servlet.RequestDispatcher;

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("/servlet6")

public class Servlet6 extends HttpServlet {

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println(request.getParameter("content"));

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

===============================================

二、过滤器

package com.fgy;

import java.io.IOException;

import javax.servlet.DispatcherType;

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(urlPatterns="*")

public class Filter2 implements Filter {

    public void destroy() {

    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

        chain.doFilter(new MyWrapper((HttpServletRequest) request), response);

    }

    public void init(FilterConfig fConfig) throws ServletException {

    }

}

=============================================

三、包装器

进行修改，实现将请求参数的值1替换为one

package com.fgy;

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");

    }

}