Spring Container 初始化 beans 的三种方式

最新推荐文章于 2024-12-23 21:48:24 发布

bird_cat

最新推荐文章于 2024-12-23 21:48:24 发布

阅读量5.1k

点赞数 2

CC 4.0 BY-SA版权

分类专栏： Spring

本文链接：https://blog.youkuaiyun.com/topwqp/article/details/8661493

Spring 专栏收录该内容

16 篇文章

订阅专栏

本文介绍了Spring3中三种不同的bean实例化方式：构造器实例化、静态工厂方法实例化及对象工厂方法实例化，并提供了详细的配置示例与验证输出。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

1：Instantiation with a constructor


 类：


 
 package com.myapp.core;

/**
 * Spring bean
 * 
 */
public class HelloWorld {
	private String name;
 
	public void setName(String name) {
		this.name = name;
	}
 
	public void printHello() {
		System.out.println("Spring 3 : Hello ! " + name);
	}
}

services.xml配置：

<?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-3.0.xsd">

  <!-- services -->

  <!-- more bean definitions for services go here -->
  
  <!-- Instantiation with a constructor -->
  <bean id="helloBean" class="com.myapp.core.HelloWorld">
		<property name="name" value="wqp" />
	</bean>
 
  <!--  Instantiation with a static factory method -->
   <bean id="clientService" class="com.myapp.core.staticfactory.ClientService" factory-method="createInstance">
	</bean>
	
	<!-- Instantiation using an instance factory method -->
	<bean id="serviceLocator" class="com.myapp.core.instancefactory.DefaultServiceLocator">
	</bean>
	
     <bean id="clientService2"  factory-bean="serviceLocator" factory-method="createClientServiceInstance">
     </bean>
     
     <bean id="accountService" factory-bean="serviceLocator" factory-method="createAccountService">
     </bean>
   
</beans>

daos.xml用来配置 persistence layer 的beans 这是预留的里面没有beans

<?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-3.0.xsd">

 

  <!-- more bean definitions for data access objects go here -->

</beans>

SpringBeans.xml 中导入了 services.xml

<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-3.0.xsd">
 
 <import resource="resource/services.xml"/>
   <import resource="resource/daos.xml"/>
</beans>

以下是执行代码：

package com.myapp.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.myapp.core.staticfactory.ClientService;

public class App {
	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext(
				"SpringBeans.xml"); 
 
		HelloWorld obj = (HelloWorld) context.getBean("helloBean");
		obj.printHello();
		
		//ClientService  clientService = (ClientService) context.getBean("clientService");
	}
}

类分布：

以下代码是用静态工厂创建对象：

一：Instantiation with a constructor 通过构造器初始化对象：

<bean id="helloBean" class="com.myapp.core.HelloWorld">
<property name="name" value="wqp" />
</bean>

二：Instantiation with a static factory method 通过静态工厂方法创建对象

package com.myapp.core.staticfactory;

/**
 *  Instantiation with a static factory method
 * @author topwqp
 *
 */
public class ClientService {
   //first  create  a private  contrutor  method;  private  responses that  only itself can  Instantiation 
	private  ClientService(){}
 
	private  static ClientService  clientService = new  ClientService();
	
	public   static  ClientService  createInstance(){
	     //when spring  container  is  startup  the  createInstance method  will be  invoked 
		 //  output  this word  a clientService  object  is  created  ohye  is  a  good  illustration
		System.out.println("a clientService  object  is  created ohye");
		 return   clientService;
	}
	
 
 
}

对应的配置：

 <!--  Instantiation with a static factory method -->
   <bean id="clientService" class="com.myapp.core.staticfactory.ClientService" factory-method="createInstance">
	</bean>

以下是通过对象工厂创建对象：

三： Instantiation using an instance factory method 通过对象工厂方法创建对象

package com.myapp.core.instancefactory;

public interface AccountService {

}

package com.myapp.core.instancefactory;

public interface ClientService {

}

package com.myapp.core.instancefactory;

public class ClientServiceImpl implements  ClientService{

}

package com.myapp.core.instancefactory;

public class AccountServiceImpl implements  AccountService{

}

工厂方法创建对象：

package com.myapp.core.instancefactory;
/**
 * Instantiation using an instance factory method
 * @author topwqp
 *
 */
public class DefaultServiceLocator {
   
	private static ClientService  clientService = new  ClientServiceImpl();
	
	private  static  AccountService  accountService = new  AccountServiceImpl();
	
	public  DefaultServiceLocator(){}
	
	public ClientService  createClientServiceInstance(){
		System.out.println("factory  instance  method  is created  clientService........");
		return  clientService;
	}
	
	public  AccountService   createAccountService(){
		System.out.println("factory instace method is  created  accountService...........");
		return    accountService;
	}
}

对应的配置：

	
	<!-- Instantiation using an instance factory method -->
	<bean id="serviceLocator" class="com.myapp.core.instancefactory.DefaultServiceLocator">
	</bean>
	
     <bean id="clientService2"  factory-bean="serviceLocator" factory-method="createClientServiceInstance">
     </bean>
     
     <bean id="accountService" factory-bean="serviceLocator" factory-method="createAccountService">
     </bean>

验证输出：

在启动spring的 spring容器装入这些对象，这样构造方法中的打印就会输出。根据打印可以看出对象均创建成功。

以上是通过maven构建项目其中 pom.xml的配置如下：

<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.myapp.core</groupId>
  <artifactId>Spring3Example</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>Spring3Example</name>
  <url>http://maven.apache.org</url>
  
  <properties>
		<spring.version>3.0.5.RELEASE</spring.version>
	</properties>
  <dependencies>
   <dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.11</version>
			<scope>test</scope>
		</dependency>
    
    <!-- Spring 3 dependencies -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>${spring.version}</version>
		</dependency>
 
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring.version}</version>
		</dependency>
    
    
    <dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
			<version>${spring.version}</version>
		</dependency>
    
    <dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		 
  <!-- JSTL --> 
	<dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>jstl</artifactId>
		<version>1.1.2</version>
	</dependency>
 
	<dependency>
		<groupId>taglibs</groupId>
		<artifactId>standard</artifactId>
		<version>1.1.2</version>
	</dependency>
	
		
  </dependencies>
 
  <build>
	  <plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-compiler-plugin</artifactId>
			<version>2.3.2</version>
			<configuration>
				<source>1.7</source>
				<target>1.7</target>
			</configuration>
		</plugin>
	  </plugins>
	</build>
</project>

REFERENCE spring IOC