自己写的一个servlet Dispatchar,便于在osgi使用

osgi中暂时不支持springmvc等mvc框架，我们每写一个方法的时候，就需要新建一个servlet，这样很麻烦，所以想自己实现一个在osgi环境下能够运行的mvc框架，模仿springmvc或者struts2的框架。

1.首先我们看看web.xml的配置。里面定义了一个servlet,去过滤所有带.do的uri,初始化参数有controller类。当容器启动的时候，会执行servlet的init方法，然后把controller类初始化。以便后来调用。

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
	http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
	<display-name></display-name>
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>

	<servlet>
		<servlet-name>dispatcher</servlet-name>
		<servlet-class>com.yyc.servlet.Dispatcher</servlet-class>
		<init-param>
			<param-name>login</param-name>
			<param-value>com.yyc.controller.Login</param-value>
		</init-param>
		<init-param>
			<param-name>main</param-name>
			<param-value>com.yyc.controller.Main</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>dispatcher</servlet-name>
		<url-pattern>*.do</url-pattern>
	</servlet-mapping>
</web-app>

2.Dispatchar.java继承了servlet,覆盖了init方法，doGet doPost方法。init把controller类实例化后放入map，如果后面有uir请求，去截取请求的uir获取里面的类，和方法名。

然后用java反射机制去执行。

package com.yyc.servlet;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

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

public class Dispatcher extends HttpServlet {
	/**
	 *
	 */
	private static final long serialVersionUID = 1L;

	Map<String , Object> controllers = new HashMap<String , Object>();

	private ServletContext application = null;//一个web应用程序对应一个ServletContext
	private ServletConfig config = null;  //一个Servlet对应一个ServletConfig

	@Override
	public void init() throws ServletException{

		//创建controller bean
		//读取web.xml配置参数 放入controllers
		application = getServletContext();
		config = getServletConfig();
		Enumeration<String> enumeration = config.getInitParameterNames();
		while(enumeration.hasMoreElements()){
			String className = enumeration.nextElement();
			//通过获取init获取参数
			BeanFactory(className, config.getInitParameter(className));
		}

		super.init();

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

		doPost(request, response);
	}
	@Override
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String uri = request.getRequestURI();
		String classMethodName = uri.substring(uri.lastIndexOf("/")+1,uri.lastIndexOf(".do"));
		String className = classMethodName.split("_")[0];
		String methodName = classMethodName.split("_")[1];
		Object controller =  controllers.get(className);
		try {
			controller.getClass().getMethod(methodName,new Class[]{HttpServletRequest.class,HttpServletResponse.class}).invoke(controller.getClass().newInstance(),new Object[]{request,response});
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	public void BeanFactory(String className,String classPath){
		try {
			Class<?> clazz = Class.forName(classPath);
			controllers.put(className, clazz.newInstance());
			System.out.println("初始化类"+className);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

}

下面是controller的类

login.java

package com.yyc.controller;

import java.io.IOException;

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

public class Login {
	public void in(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		System.out.println("登陆！");
		response.sendRedirect("index.jsp");
	}

	public void out(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.getWriter().print("you  logout!");
		System.out.println("退出！");
	}
}

main.java

package com.yyc.controller;

import java.io.IOException;

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

public class Main {
	public void index(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		System.out.println("进入主页！");
	}
}

3.测试调用，使用的是tomcat

启动后，可以这样调用：

http://localhost:8080/dispatcher/login_in.do  login需要对应web.xml里面的servlet对应参数的值，in是对应类里面的方法名

http://localhost:8080/dispatcher/login_out.do

http://localhost:8080/dispatcher/main_index.do

这里实现了最简单的分发功能，目的是减少多余的配置 ，下次研究osgi‘  blueprint里面进行配置处理，以及依赖注入

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