Java进阶知识18 Spring对象依赖关系的几种写法

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

     <!-- 1、set方法注入值（依赖），层层分离 -->
     <!-- Dao层 --> <!-- 无参构造器用：property  有参构造器用：constructor-arg -->
     <bean id="userDao1" class="com.bw.dao.UserDao">
         <property name="name" value="Huang Long"></property>
     </bean>
     <!-- service层 -->
     <bean id="userService1" class="com.bw.service.UserService">
         <property name="userDao" ref="userDao1"></property>
     </bean>
     <!-- Action层、多例-->
     <bean id="userAction1" class="com.bw.action.UserAction" scope="prototype">
         <property name="userService" ref="userService1"></property>
     </bean>
     <!-- ========================================================================== -->

     <!-- 2、set方法注入值（依赖），层层嵌套 -->
     <bean id="userAction2" class="com.bw.action.UserAction">
         <property name="userService">
             <bean class="com.bw.service.UserService">
                 <property name="userDao">
                     <bean class="com.bw.dao.UserDao">
                         <property name="name"><value>Huang Long</value></property>
                     </bean>
                 </property>
             </bean>
         </property>
     </bean>
     <!-- ========================================================================== -->

     <!-- 3、p名称空间 ,头部要引入xmlns:p="http://www.springframework.org/schema/p"-->
     <!-- Dao层 -->
     <bean id="userDao3" class="com.bw.dao.UserDao">
         <property name="name" value="Huang Long"></property>
     </bean>
     <!-- service层 -->
     <bean id="userService3" class="com.bw.service.UserService" p:userDao-ref="userDao3"></bean>
     <!-- Action层、多例-->
     <bean id="userAction3" class="com.bw.action.UserAction" p:userService-ref="userService3" scope="prototype"></bean>
 </beans>

下面两种方式，不建议使用：

1、自动装配

 <?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:aop="http://www.springframework.org/schema/aop"
        xmlns:tx="http://www.springframework.org/schema/tx"
        xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd">
        <!--  default-autowire="byName" 可以配置全局自动装配 -->

     <!-- 4、自动装配（局部） --> <!-- 自动装配方式，不建议使用，1、增加服务器负担；2、大项目不好维护 -->
     <!-- Dao层 -->
     <bean id="userDao" class="com.bw.dao.UserDao">
         <property name="name" value="Huang Long"></property>
     </bean>

     <!-- service层 -->
     <bean id="userService" class="com.bw.service.UserService" autowire="byName"></bean>

     <!-- Action层、多例-->
     <bean id="userAction4" class="com.bw.action.UserAction" autowire="byName" scope="prototype"></bean>
 </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"
        xmlns:aop="http://www.springframework.org/schema/aop"
        xmlns:tx="http://www.springframework.org/schema/tx"
        xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd" default-autowire="byName">
        <!--  default-autowire="byName" 可以配置全局自动装配 -->

     <!-- 4、自动装配（全局） --> <!-- 自动装配方式，不建议使用，1、增加服务器负担；2、大项目不好维护 -->
     <!-- Dao层 -->
     <bean id="userDao" class="com.bw.dao.UserDao">
         <property name="name" value="Huang Long"></property>
     </bean>

     <!-- service层 -->
     <bean id="userService" class="com.bw.service.UserService" ></bean>

     <!-- Action层、多例-->
     <bean id="userAction4" class="com.bw.action.UserAction" scope="prototype"></bean>
 </beans>

2、注解  （省略）

原创作者：DSHORE

作者主页：http://www.cnblogs.com/dshore123/

原文出自：https://www.cnblogs.com/dshore123/p/11704218.html

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