Guice 学习（九） WEB AND SERVLET

本文主要是介绍Guice 学习（九） WEB AND SERVLET，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1、新建web工程，导入JAR包

这里写图片描述

2、配置web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5" 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_2_5.xsd"><display-name>GuiceWeb</display-name><listener><listener-class>com.guice.web.listener.MyGuiceServletContextListener</listener-class></listener><filter><filter-name>guiceFilter</filter-name><filter-class>com.google.inject.servlet.GuiceFilter</filter-class></filter><filter-mapping><filter-name>guiceFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping></web-app>

3、自定义监听器

package com.guice.web.listener;import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.servlet.GuiceServletContextListener;
import com.google.inject.servlet.ServletModule;
import com.guice.web.servlet.HelloWorldServlet;public class MyGuiceServletContextListener extends GuiceServletContextListener {@Overrideprotected Injector getInjector() {return Guice.createInjector(new ServletModule() {protected void configureServlets() {serve("/helloworld").with(HelloWorldServlet.class);}});}
}

4、新建servlet

package com.guice.web.servlet;import java.io.IOException;
import java.util.Date;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Singleton;
import com.guice.web.service.HelloWorld;/*** TODO :每个servlet必须是单例的* * @author E468380*/
@Singleton
public class HelloWorldServlet extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.getWriter().append("Hello , Guice !" + new Date());}}

5、运行tomcat服务器

一个简单的Helloworld

6、注入服务

新建service接口

package com.guice.web.service;import java.io.IOException;import com.google.inject.ImplementedBy;@ImplementedBy(HelloWorldImpl.class)
public interface HelloWorld {void execute() throws IOException;
}

新建实现类

package com.guice.web.service;import java.io.IOException;
import java.util.Date;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.google.inject.Inject;public class HelloWorldImpl implements HelloWorld {private HttpServletRequest request;private HttpServletResponse response;@Injectpublic HelloWorldImpl(HttpServletRequest request, HttpServletResponse response) {super();this.request = request;this.response = response;}public void execute() throws IOException {String name = request.getParameter("user");if (name == null || name.length() < 1)name = "Guest";response.getWriter().append(String.format("Hello, %s. %s -> sessionId=%s,hashCode=%d ", name, new Date(), request.getSession().getId(), hashCode()));}
}

修改servlet

package com.guice.web.servlet;import java.io.IOException;
import java.util.Date;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Singleton;
import com.guice.web.service.HelloWorld;/*** TODO :每个servlet必须是单例的* * @author E468380*/
@Singleton
public class HelloWorldServlet extends HttpServlet {private static final long serialVersionUID = 1L;@Injectprivate Injector inj;// 自动注入Injector对象，然后通过Inject对象获取我们的服务，@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.getWriter().append("Hello , Guice !" + new Date());inj.getInstance(HelloWorld.class).execute();inj.getInstance(HelloWorld.class).execute();}}

输出

Hello , Guice !Thu Jul 02 10:38:27 CST 2015
Hello, Guest. Thu Jul 02 10:38:27 CST 2015 -> sessionId=C038A844F4C2C8259E06479AA59F0CC7,hashCode=1240584990 
Hello, Guest. Thu Jul 02 10:38:27 CST 2015 -> sessionId=C038A844F4C2C8259E06479AA59F0CC7,hashCode=593198207

由上可知：sessionId是一样的，但是hashcode值不同，与原例不符，那是因为在
原文示例中（参考这里）将HelloWorldImpl类上标明注解：@RequestScoped ，但是程序运行会出如下错误：

HTTP Status 500 - Filter execution threw an exceptiontype Exception reportmessage Filter execution threw an exceptiondescription The server encountered an internal error that prevented it from fulfilling this request.exceptionjavax.servlet.ServletException: Filter execution threw an exceptionroot causejava.lang.NoSuchMethodError: com.google.inject.Scopes.isCircularProxy(Ljava/lang/Object;)Zcom.google.inject.servlet.ServletScopes$2$1.get(ServletScopes.java:121)com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:40)com.google.inject.internal.InjectorImpl$3.get(InjectorImpl.java:737)com.google.inject.internal.InjectorImpl$4$1.call(InjectorImpl.java:978)com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1024)com.google.inject.internal.InjectorImpl$4.get(InjectorImpl.java:974)com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1013)com.guice.web.servlet.HelloWorldServlet.doGet(HelloWorldServlet.java:34)javax.servlet.http.HttpServlet.service(HttpServlet.java:620)javax.servlet.http.HttpServlet.service(HttpServlet.java:727)com.google.inject.servlet.ServletDefinition.doServiceImpl(ServletDefinition.java:278)com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:268)com.google.inject.servlet.ServletDefinition.service(ServletDefinition.java:180)com.google.inject.servlet.ManagedServletPipeline.service(ManagedServletPipeline.java:93)com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:120)com.google.inject.servlet.GuiceFilter$1.call(GuiceFilter.java:132)com.google.inject.servlet.GuiceFilter$1.call(GuiceFilter.java:129)com.google.inject.servlet.GuiceFilter$Context.call(GuiceFilter.java:206)com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:129)