WEB应用通过Spring注入实现类

╰半夏微凉° 2022-09-19 15:18 116阅读 0赞

众所周知Spring实现了控制反转和依赖注入

下面以一简单Web应用来说明如何通过Spring注入实现类代码如下

**代码1:IDateFormat**  
//接口定义  
package com.doit8.common.util;  
public interface IDateFormat \{  
 public String getNowDate();  
\}  
  
**代码2:DateFormatImpl**  
//实现类,该实现类作用只是取得当前日期并格式化它.  
package com.doit8.common.util;  
import java.text.SimpleDateFormat;  
import java.util.Date;  
public class DateFormatImpl implements IDateFormat\{  
 public String getNowDate() \{  
  Date date=new Date();  
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");  
  String dateString = formatter.format(date);  
  return dateString;  
 \}  
\}  
  
**代码3:MyBeanFactory**  
//Bean工产通过Spring取得注入的实现类方法,通过传入的request取得Web应用的上下文环境  
package com.doit8.common.util;

import javax.servlet.ServletContext;  
import javax.servlet.http.HttpServletRequest;  
import org.springframework.beans.factory.BeanFactory;  
import org.springframework.web.context.support.WebApplicationContextUtils;  
import org.springframework.web.servlet.support.RequestContextUtils;

public class MyBeanFactory \{  
 private static BeanFactory overrideFactory = null;  
 private static BeanFactory factory = null;  
 /\*\*  
  \* 获取spring实例  
  \* @return  
  \* @throws InstantiationException  
  \*/  
 public static Object getInstance(HttpServletRequest request,String beanName) throws InstantiationException \{  
  try \{  
   if (overrideFactory != null) \{  
    Object reply = overrideFactory.getBean(beanName);  
    return reply;  
   \}  
   if (factory == null) \{  
    factory = getBeanFactory(request);  
    overrideFactory = factory;  
   \}  
   Object reply = factory.getBean(beanName);  
   return reply;  
  \} catch (RuntimeException ex) \{  
   throw ex;  
  \} catch (Exception ex) \{  
   throw new InstantiationException(ex.toString());  
  \}  
 \}  
 /\*\*  
  \* 获取spring bean工厂  
  \*  
  \* @return  
  \*/  
 private static BeanFactory getBeanFactory(HttpServletRequest request) \{  
  ServletContext srvCtx = request.getSession().getServletContext();  
  if (request != null) \{  
   return RequestContextUtils.getWebApplicationContext(request, srvCtx);  
  \} else \{  
   return WebApplicationContextUtils.getWebApplicationContext(srvCtx);  
  \}  
 \}  
\}

**代码4:TestLoadClass**  
//取得注入实现类的JAVABEAN  
package test;  
import javax.servlet.http.HttpServletRequest;  
import com.doit8.common.util.DateFormatImpl;  
import com.doit8.common.util.IDateFormat;  
import com.doit8.common.util.MyBeanFactory;  
public class TestLoadClass \{  
 IDateFormat datefomat;  
 private String datestr;  
 public TestLoadClass(HttpServletRequest request)  
 \{  
  try \{  
   //根据Spring配置的BeanName取得实现类(Spring配置见下配置文件)  
   datefomat=(DateFormatImpl)MyBeanFactory.getInstance(request,"DateFormat");  
   datestr=datefomat.getNowDate();  
  \} catch (InstantiationException e) \{  
   // TODO Auto-generated catch block  
   e.printStackTrace();  
  \}  
 \}  
 public String getDate()  
 \{  
  return datestr;  
 \}  
\}  
  
**配置文件1:web.xml**  
需要在web.xml文件中指定Spring的配置文件侦听类  
<?xml version="1.0" encoding="UTF-8"?>  
<web-app version="2.4"  
 xmlns="[http://java.sun.com/xml/ns/j2ee][http_java.sun.com_xml_ns_j2ee]"  
 xmlns:xsi="[http://www.w3.org/2001/XMLSchema-instance][http_www.w3.org_2001_XMLSchema-instance]"  
 xsi:schemaLocation="[http://java.sun.com/xml/ns/j2ee][http_java.sun.com_xml_ns_j2ee]  
 [http://java.sun.com/xml/ns/j2ee/web-app\_2\_4.xsd][http_java.sun.com_xml_ns_j2ee_web-app_2_4.xsd]">  
   <context-param>  
  <param-name>contextConfigLocation</param-name>  
  <param-value>/WEB-INF/applicationContext.xml</param-value>  
 </context-param>  
 <listener>  
  <listener-class>  
   org.springframework.web.context.ContextLoaderListener  
  </listener-class>  
 </listener>  
</web-app>  
  
**配置文件2:****applicationContext.xml**  
该配置文件指定实现类  
<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "[http://www.springframework.org/dtd/spring-beans.dtd][http_www.springframework.org_dtd_spring-beans.dtd]">  
<beans>  
 <bean id="DateFormat" class="com.doit8.common.util.DateFormatImpl">  
 </bean>  
</beans>  
  
完成以上配置后就可以在Web应用中用到Spring配置中配置的实现类了。见下JSP代码  
<%@ page language="java"  pageEncoding="UTF-8"%>  
<%@ page import="test.TestLoadClass"%>  
<%  
String path = request.getContextPath();  
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
%>  
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
<html>  
  <head>  
    <base href="<%=basePath%>">  
    <title>My JSP 'testjsp.jsp' starting page</title>  
    <meta http-equiv="pragma" content="no-cache">  
    <meta http-equiv="cache-control" content="no-cache">  
    <meta http-equiv="expires" content="0">  
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
    <meta http-equiv="description" content="This is my page">  
  </head>

运行结果在页面上显示当前格式化后的日期

[http_java.sun.com_xml_ns_j2ee]: http://java.sun.com/xml/ns/j2ee
[http_www.w3.org_2001_XMLSchema-instance]: http://www.w3.org/2001/XMLSchema-instance
[http_java.sun.com_xml_ns_j2ee_web-app_2_4.xsd]: http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd
[http_www.springframework.org_dtd_spring-beans.dtd]: http://www.springframework.org/dtd/spring-beans.dtd