Programming Design Notes

Servlet 3.0 的新功能
類似 Spring Framework 的 Web MVC使用 Java Annotation 來擴展 Servlet
廢話不多說
看例子
先來看舊的設定方法

IndexServlet

package com.test.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Index
 */

public class IndexServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public IndexServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        PrintWriter out = response.getWriter();
        out.println("Servlet hello world!");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

MyFilter

package com.test.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;

/**
 * Servlet Filter implementation class MyFilter
 */

public class MyFilter implements Filter {

    /**
     * Default constructor.
     */
    public MyFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here
        PrintWriter out = response.getWriter();
        out.println("MyFilter hello world!");
        // pass the request along the filter chain
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
    <display-name>TestWAR</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
        <welcome-file>index</welcome-file>
    </welcome-file-list>
    <servlet>
        <description></description>
        <display-name>IndexServlet</display-name>
        <servlet-name>IndexServlet</servlet-name>
        <servlet-class>com.test.servlet.IndexServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>IndexServlet</servlet-name>
        <url-pattern>/index</url-pattern>
    </servlet-mapping>
    <filter>
        <display-name>MyFilter</display-name>
        <filter-name>MyFilter</filter-name>
        <filter-class>com.test.filter.MyFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>MyFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

結果顯示:
MyFilter hello world!
Servlet hello world!

舊有的設定方式需要在 web.xml 設定好 Servlet 和 Filter 才可以
現在看看新的設定方式

IndexServlet

package com.test.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;

/**
 * Servlet implementation class Index
 */
@WebServlet(name = "Index", urlPatterns = { "/index" })
public class IndexServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public IndexServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        PrintWriter out = response.getWriter();
        out.println("Servlet annotation work!");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

MyFilter

package com.test.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;
import javax.servlet.annotation.WebFilter;

/**
 * Servlet Filter implementation class MyFilter
 */
@WebFilter(filterName = "MyFilter", urlPatterns = { "/*" })
public class MyFilter implements Filter {

    /**
     * Default constructor.
     */
    public MyFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here
        PrintWriter out = response.getWriter();
        out.println("MyFilter annotation work!");
        // pass the request along the filter chain
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
    <display-name>TestWAR</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
        <welcome-file>index</welcome-file>
    </welcome-file-list>
</web-app>

結果顯示:
MyFilter annotation work!
Servlet annotation work!

IndexServlet 加入了

@WebServlet(name="Index", urlPatterns={"/index"})

MyFilter 加入了

@WebFilter(filterName="MyFilter", urlPatterns={"/*"})

設定交由各自的 Class 去設定
web.xml 完全不需要設定 Servlet 和 Filter
方便多了
如果你不喜歡這樣的設定方式也可以用回舊有的設定方法

雖然 Servlet 3.0 多了這個好用的東西
但還是比不上 Spring Framework 的注解方式(Annotation) 好用 (純粹個人意見)

WAR 檔案(連原始碼): TestWar.war

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