spring step 2 : 又见hello world！

1.开发环境

myeclipse 8.5 tomcat 5.5 jdk 1.6

2.又见hello world之j2se版。

http://kin111.blog.51cto.com/738881/171031/

通过xml对beans的描述，使用spring框架动态的反射出所需要的实体类。

首先使用myeclipse新建一个web工程，然后添加spring Capabilities。将自动生成的applicationContext.xml放在src目录中。新建两个类：HelloWorld和SpringClient.代码如下：

/**
 * 
 * @author jefferyxu
 *
 */
public class HelloWorld {
	public void sayHello () {
		System.out.println("Hello World!");
	}
}

/**
 * 
 * @author jefferyxu
 *
 */

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringClient {
	public static void main(String[] args) {
		ApplicationContext applicationContext = 
			new ClassPathXmlApplicationContext("applicationContext.xml");
		
		// 这里需要和配置文件中的名字相对应
		HelloWorld hello = (HelloWorld)applicationContext.getBean("sayHello");
	
		hello.sayHello();
		
	}
}

applicationContext.xml文件:

<?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:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<!-- 这里添加自己的beans -->
<bean id="sayHello" class="HelloWorld"></bean>

</beans>

文件的目录结构如下：

直接运行SpringClient，可能产生如下的warnings:

log4j:WARN No appenders could be found for logger (org.springframework.context.support.ClassPathXmlApplicationContext).
log4j:WARN Please initialize the log4j system properly.

解决的办法就是src目录中添加log4j.properties 文件。文件内容如下：

log4j.rootLogger=INFO, stdout, logfile

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n

log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.File=${ideashopx.root}/WEB-INF/logs/ideashopx.log
log4j.appender.logfile.MaxFileSize=1024KB
# Keep three backup files.
log4j.appender.logfile.MaxBackupIndex=3
# Pattern to output: date priority [category] - message
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

再次运行SpringClient程序，程序只是简单的输出hello world这个亲切的字符串。

3.hello world之j2ee web版。

http://maestric.com/doc/java/spring/hello_world

In 'WEB-INF/web.xml', we declare Spring DispatcherServlet and map '*.html' URLs to it:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
         http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
 
  <servlet>
    <servlet-name>springmvc</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>springmvc</servlet-name>
    <url-pattern>*.html</url-pattern>
  </servlet-mapping>
 
  <welcome-file-list>
    <welcome-file>
      jsp/index.jsp
    </welcome-file>
  </welcome-file-list>
 
</web-app>

Let's now create the Spring configuration file 'WEB-INF/springmvc-servlet.xml' (name based on the servlet name above):

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
  <bean name="/hello_world.html" class="springmvc.web.HelloWorldController"/>
 
  <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
      <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
      <property name="prefix" value="/jsp/"/>
      <property name="suffix" value=".jsp"/>
  </bean>
 
</beans>

Map URL /hello_world.html to Controller HelloWorldController
Declare View Resolver: when view 'view_name' is called (from the Controller), the file '/jsp/view_name.jsp' will be used

在myeclipse中可以使用下面的方法生成简单的模板：

Let's create the Controller 'WEB-INF/src/springmvc/web/HelloWorldController.java':

package springmvc.web;
 
import java.io.IOException;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;
 
public class HelloWorldController implements Controller {
 
	public ModelAndView handleRequest(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
 
		String aMessage = "Hello World MVC!";
 
		ModelAndView modelAndView = new ModelAndView("hello_world");
		modelAndView.addObject("message", aMessage);
 
		return modelAndView;
	}
}

Now the view: 'jsp/hello_world.jsp':

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<body>
	<p>This is my message: ${message}</p>
</body>
</html>

将整个的web工程deploy之后，打开：http://localhost:8180/springmvc/hello_world.html，如果一切正常的话，将显示“

This is my message: Hello World MVC!”字符串（由controller传递给页面）。

spring的hello world完毕，其中的主要意义是了解整个spring开发流程，忽略了其中的很多的细节的问题。