作用域、延迟加载、数据装配与包扫描的方式创建bean

一、作用域

• 容器内部默认使用的是单例模式
  • 两种模式
    • 单例模式

        <bean id ="SomeService" class="org.example.SomeService" scope="singleton" ></bean> 
        # 备注
          # scope= "singleton" 单例模式，默认
          # scope= "prototype" 单例模式，默认
      

    • 多例模式

      <bean id ="SomeService" class="org.example.SomeService" scope="prototype" ></bean> 
      

二、延迟加载

    <bean id ="SomeService" class="org.example.SomeService" scope="prototype" lazy-init="true"></bean>
    # 备注
      # lazy-init="true" 什么时候用对象，什么时候创建对象

三、类型装配

• 值类型装配
  • application.xml

        <?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.xsd">
            <bean id ="SomeService" class="org.example.SomeService" scope="prototype" lazy-init="true">
               
                 <constructor-arg name="name" value="xiaoming"></constructor-arg>
        
            </bean>
    
    

    import java.util.List;
    
    public interface ISomeService {
        void doSome(); 
    }

  ```

• 实现类

    package org.example;
  
    import java.util.List;
    
    public class SomeService implements ISomeService{
       
        private String name;
        
        public SomeService (String name)
        {
            this.name = name;
        }
        @Override
        public void doSome() {
            System.out.println("SomeService ----name值："+name);
        }
    
      
    }
  
  

• main

    ApplicationContext context =  new ClassPathXmlApplicationContext("applicationContext.xml");
    ISomeService iSomeService =  context.getBean("SomeService",ISomeService.class); 
    iSomeService.doSome();
  

• 引用类型装配
  • application.xml

      <?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.xsd">
          <bean id ="SomeService" class="org.example.SomeService" scope="prototype" lazy-init="true">
              <property name="lists">
                  <list>
                      <value>1</value>
                      <value>2</value>
                      <value>3</value>
                      <value>4</value>
                  </list>
              </property> 
      
          </bean>
      
      </beans>
    

  • 接口类

      package org.example;
    
      import java.util.List;
      
      public interface ISomeService { 
          List<String> getList();
      }
    
    

  • 实现类

    package org.example;
    
      import java.util.List;
      
      public class SomeService implements ISomeService{
          private List<String> lists; 
          public void setLists(List<String> lists) {
              this.lists = lists;
          }
       
      
          @Override
          public List<String> getList() {
              return lists;
          }
      } 
    

  • main

      package org.example;
    
      import org.springframework.context.ApplicationContext;
      import org.springframework.context.support.ClassPathXmlApplicationContext;
      
      public class Main {
          /**
           * main
           * @param args
           */
          public static void main(String[] args) {
              ApplicationContext context =  new ClassPathXmlApplicationContext("applicationContext.xml");
              ISomeService iSomeService =  context.getBean("SomeService",ISomeService.class);
              System.out.println(iSomeService.getList()); 
          }
      }
    

四、包扫描的方式创建bean

• applicationContextScanning.xml

    <?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"
          xsi:schemaLocation="
              http://www.springframework.org/schema/beans
              http://www.springframework.org/schema/beans/spring-beans.xsd
              http://www.springframework.org/schema/context
              http://www.springframework.org/schema/context/spring-context.xsd">
       <context:component-scan base-package="com.scanningPackage"/>
   </beans>

• 接口类

       package com.scanningPackage;
  
       public interface ISomeService {
           void doSome();
       }
  
  

• 实现类

       package com.scanningPackage;
  
       import org.springframework.stereotype.Service;
       
       @Service
       public class SomeService implements ISomeService{
           @Override
           public void doSome() {
               System.out.println("SomeService--doSome");
           }
       }
  
  

  • 注解注入
    • @Repository
      • 主要标记在数据访问层对应的实现类
    • @Service
      • 主要标记在业务逻辑层对应的实现类
    • @Controller
      • 主要标记在控制层对应的实现类
    • @Component
      • 不清楚该层数据哪一类
    • @Autowired [spring 框架提供的]
      • 使用该注解完成依赖注入
    • @Resource [java 提供]
      • 使用该注解完成依赖注入
• main

  package com.scanningPackage;
  
   import org.springframework.context.ApplicationContext;
   import org.springframework.context.support.ClassPathXmlApplicationContext;
   
   public class Test {
       private static ISomeService iSomeService;
       public static void main(String[] agrs) {
           ApplicationContext context =  new ClassPathXmlApplicationContext("applicationContextScanning.xml");
           iSomeService = context.getBean("someService",ISomeService.class);
           iSomeService.doSome();
       }
   }