java 过滤器Filter中chain.doFilter()之前和之后代码的执行顺序

过滤器拦截到请求之后，首先是执行doFilter()方法中chain.doFilter()之前的代码，然后放弃权限给下一个过滤器或者serverlet等等，最后才执行chain.doFilter()之后的代码。

测试场景：

1.新建一个index.html，配置连接调整到一个test.jsp页面

2.对test.jsp做两层过滤，查看过滤器代码中chain.doFilter()之前和之后代码的执行顺序。

过滤器一：(使用注解控制过滤器执行顺序，此处先执行过滤器一，在执行过滤器2)

@WebFilter(filterName="firstFilter0",urlPatterns="/test.jsp")
public class FirstFilter implements Filter {

	@Override
	public void destroy() {
		System.out.println("first destroy...");
	}

	@Override
	public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
			throws IOException, ServletException {
		System.out.println("1. first doFilter...");
		arg2.doFilter(arg0, arg1);
		System.out.println("2. first doFilter...");
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("first init...");
	}

}

过滤器二：

@WebFilter(filterName="firstFilter1",urlPatterns="/test.jsp")
public class SecondFilter implements Filter {

	@Override
	public void destroy() {
		System.out.println("second destroy...");
	}

	@Override
	public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
			throws IOException, ServletException {
		System.out.println("3. second doFilter...");
		arg2.doFilter(arg0, arg1);
		System.out.println("4. second doFilter...");
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		System.out.println("second init...");
	}

}

index.html:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

  <a href="test.jsp">To Test Page</a>

</body>
</html>

test.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

<h4>Test Page</h4>
<%
  System.out.println("5. Test Page");
%>

</body>
</html>

在浏览器输入http://localhost:8080/day_38/index.html控制台将打印如下内容 :

1. first doFilter...
3. second doFilter...
5. Test Page
4. second doFilter...
2. first doFilter...

java 过滤器Filter中chain.doFilter()之前和之后代码的执行顺序

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