使用Spring4+Maven构建webapp项目

转载地址：http://blog.csdn.net/binyao02123202/article/details/20387595

一.需求

使用spring去管理web项目,是目前非常流行的一种思路,本文将介绍使用maven+spring 4.0.2 来构建一个简单的web项目.

 

二.实现

1.新建一个maven项目,如下图所示:

 

 

这里因为是构建web项目,所以,选择的是webapp.

项目的架构图:



 

 

2.在pom.xml中添加所依赖的jar包,如下所示:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>com.amos</groupId>
<artifactId>ssh_integrated</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>ssh_integrated Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>4.0.2.RELEASE</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>4.0.2.RELEASE</version>
</dependency>
</dependencies>
<build>
<finalName>ssh_integrated_spring</finalName>
</build>
</project>

 

3.新建一个接口com.amos.service.IHello.java,并实现接口.

package com.amos.service;

public interface IHello {

public String sayHi();

}

com.amos.service.HelloImpl.Java

package com.amos.service;

import java.util.Date;

public class HelloImpl implements IHello{
private String msg;
public void setMsg(String msg) {
this.msg = msg;
}

public String sayHi() {

return "当前时间:"+new Date()+" msg:"+msg;
}

}

 

4.新建一个Servlet,并实现此Servlet

com.amos.web.HelloServlet

package com.amos.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import com.amos.service.IHello;
@WebServlet(name="HelloServlet",urlPatterns={"/hello"})
public class HelloServlet extends HttpServlet {
private static final long serialVersionUID = 2801654413247618244L;
private IHello hello;

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

//方法1,使用传统方式去加载beans.xml,每次请求时加载
//ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");

//方法2,使用监听器的方式加载beans.xml,在一启动的时候就加载监听器,避免多次加载,提高效率
//ApplicationContext applicationContext  = (ApplicationContext) this.getServletContext().getAttribute("SpringApplicationContext");

//方法3,使用spring自带的监听器去加载beans.xml
//ApplicationContext applicationContext  = (ApplicationContext) this.getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
//使用webapplicationcontextutils这个工具类可以很方便的获取ApplicationContext,只需要传入servletContext
ApplicationContext applicationContext = WebApplicationContextUtils.getRequiredWebApplicationContext(this.getServletContext());

hello = applicationContext.getBean(IHello.class);
String sayHi = hello.sayHi();
System.err.println("sayHi:" + sayHi);
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write("<h2>" + sayHi + "</h2>");
}
}

注:这里要注意的是实现spring管理Bean的三种方式.

第一种:最传统的方式,同时也是效率最低的一种,因为,每次发一个请求都要重新加载一次,而且对于不同的Servlet的要每个都去加载,会大大降低效率.

第二种:使用监听器来实现加载beans.xml,每次项目启动的时候加载一次就可以了.这样大提高了效率.

com.amos.web.InitSpringFactoryListener.java

package com.amos.web;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class InitSpringFactoryListener implements ServletContextListener {
public InitSpringFactoryListener() {
}

public void contextInitialized(ServletContextEvent arg0) {
//这里将加载beans.xml加载到内存中,放到servletcontext中,名称可以随便取,这里取为SpringApplicationContext,
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
arg0.getServletContext().setAttribute("SpringApplicationContext", applicationContext);
}
public void contextDestroyed(ServletContextEvent arg0) {
}
}

 

同时,web.xml中要定义一个listener属性.

<!-- 自己去写一个监听器来实现加载beans.xml,进而启动spring容器 -->
<!--
<listener>
<listener-class>com.amos.web.InitSpringFactoryListener</listener-class>
</listener> -->

 

第三种:针对第二种方法,其实spring中已经封装好了一种监听器,人工去配置即可,原理和第二种方法一致.

 

只需要在web.xml中加入如下代码即可.

<!-- 使用spring自带的监听器,其默认加载的是WEB-INF下的applicationContext.xml -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

但运行进会报如下错误:

org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from ServletContext resource [/WEB-INF/applicationContext.xml]; nested exception is java.io.FileNotFoundException: Could not open ServletContext resource [/WEB-INF/applicationContext.xml]
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:343)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:303)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:216)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:187)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:129)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:540)
........
Caused by: java.io.FileNotFoundException: Could not open ServletContext resource [/WEB-INF/applicationContext.xml]
at org.springframework.web.context.support.ServletContextResource.getInputStream(ServletContextResource.java:141)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:329)
... 22 more

说找不到applicationContext.xml文件,那么如何解决这个问题呢?

他说找不到,那就在WIB-INF目录下建一个即可.

然后引入自定义的beans.xml即可.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd ">
<import resource="classpath:beans.xml"/>
</beans>

这个时候问题解决.

这里HelloSerlvet中如何获取对应的ApplicationContext呢?

//方法3,使用spring自带的监听器去加载beans.xml
//ApplicationContext applicationContext  = (ApplicationContext) this.getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);

这个是需要查看源码才能发现其属性名称,所以比较麻烦.这里还有一种较简便的方法,如下所示:

//使用webapplicationcontextutils这个工具类可以很方便的获取ApplicationContext,只需要传入servletContext
ApplicationContext applicationContext = WebApplicationContextUtils.getRequiredWebApplicationContext(this.getServletContext());

第三种方法,基本上配置完毕,但还会感觉很不爽,因为还要新建一个applicationContext.xml去专门import bean.xml,是相当讨厌的.

其实还可以在web.xml中配置自定义的xml文件名称,如下所示:

<!-- 配置spring的加载文件路径及文件名称 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:beans.xml</param-value>
</context-param>

 

org.springframework.web.context.ContextLoaderListener中有这样一段说明:

<p>Processes a {@link #CONFIG_LOCATION_PARAM "contextConfigLocation"}
* context-param and passes its value to the context instance, parsing it into
* potentially multiple file paths which can be separated by any number of
* commas and spaces, e.g. "WEB-INF/applicationContext1.xml,
* WEB-INF/applicationContext2.xml". Ant-style path patterns are supported as well,
* e.g. "WEB-INF/*Context.xml,WEB-INF/spring*.xml" or "WEB-INF/**/*Context.xml".
* If not explicitly specified, the context implementation is supposed to use a
* default location (with XmlWebApplicationContext: "/WEB-INF/applicationContext.xml").
*

可以自定义spring默认加载的xml文件的名称,可以以逗号和空格进行分隔,也可以使用Ant类型的去标记.xml如,WEB-INF/spring*.xml

否则默认的加载的就是applicationContext.xml.

可以在web.xml中进行配置其参数.

所以,最终的web.xml如下:

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
<display-name>Archetype Created Web Application</display-name>
<!-- 配置spring的加载文件路径及文件名称 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:beans.xml</param-value>
</context-param>

<!-- 使用spring自带的监听器,其默认加载的是WEB-INF下的applicationContext.xml -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<!-- 自己去写一个监听器来实现加载beans.xml,进而启动spring容器 -->
<!--
<listener>
<listener-class>com.amos.web.InitSpringFactoryListener</listener-class>
</listener> -->
</web-app>

 

5.运行效果

6.本文源码

 

https://github.com/amosli/ssh_integrated_spring