Tomcat：为Filter过滤器设置参数

使用netbeans8创建web项目HelloJSP，项目完成时结构如下：

web.xml内容如下：

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <filter>
        <filter-name>FirstFilter</filter-name>
        <filter-class>letian.filter.FirstFilter</filter-class>
        <init-param>  
            <param-name>name1</param-name>  
            <param-value>letian1</param-value>  
        </init-param>  
        <init-param>  
            <param-name>name2</param-name>  
            <param-value>letian2</param-value>  
        </init-param> 
    </filter>
    <filter-mapping>
        <filter-name>FirstFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    
</web-app>

可以看到，过滤器FirstFilter有两个参数name1和name2，值分别是letian1、letian2。

letian/filter/FirstFilter.java内容如下：

package letian.filter;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FirstFilter implements Filter {
    
    private String filterName;
    private String name1;
    private String name2;
    
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterName = filterConfig.getFilterName();
        this.name1 = filterConfig.getInitParameter("name1");
        this.name2 = filterConfig.getInitParameter("name2");
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        
        System.out.println("filterName:"+filterName);
        System.out.println("name1:"+name1);
        System.out.println("name2:"+name2);
        
        chain.doFilter(request, response);
 
    }
    
    public void destroy() { }
}

letian/servlet/Home.java内容如下：

package letian.servlet;

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(name = "Home", urlPatterns = {"/"})
public class Home extends HttpServlet {
    
    
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("I am home!"); // 输出到控制台
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {
            out.println("<h1>Hello</h1>");
        }
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }


    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }


}

效果：

启动tomcat 8后，访问http://localhost:8080/HelloJSP/，可以看到tomcat输出：

filterName:FirstFilter
name1:letian1
name2:letian2
I am home!

参考：

http://blog.csdn.net/home_zhang/article/details/7754634