【spring框架】AutoWire自动装配

看我们配置的beans.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-2.5.xsd">


  <bean id="userDao" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="1"></property>
  </bean>
  <bean id="userDao2" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="2"></property>
  </bean>
  
  <bean id="userService" class="cn.edu.hpu.service.UserService" >
    <property name="userDao" ref="u" />
  </bean>
  
</beans>

在默认的情况下，我们会手动设定userService所引用的bean：<property name="userDao" ref="u" />，但是我们也可以不指定，由spring来帮我们自动确定，这个叫做AutoWire，自动装配。

设置方法：

<bean id="userService" class="cn.edu.hpu.service.UserService" scope="prototype" autowire="default">
 </bean>

即在bean属性栏里加 autowire="XXX"的属性， autowire有以下几个参数可以设定:

no、byType、byName、default(常用的是这四个)

默认的是no，即需要手动来设定。

byName是按照名字去匹配。

byType是按照类型去匹配。

default是指定你在<beans...中设定的 default-autowire="XXX"

byName测试:

beans.xml中设置:

<bean id="userService" class="cn.edu.hpu.service.UserService" scope="prototype" autowire="byName">
 </bean>

UserDaoImpl.java:

package cn.edu.hpu.dao.Impl;


import java.util.List;
import java.util.Map;
import java.util.Set;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserDaoImpl implements UserDao{


  private int daoId;
  
  
  public int getDaoId() {
    return daoId;
  }




  public void setDaoId(int daoId) {
    this.daoId = daoId;
  }




  public void save(User u) {
      System.out.println("add success!!");    
  }




  @Override
  public String toString() {
    
    return "daoid="+daoId;
  }
}

改写了toString方法，打印daoId，看看下面注入了哪个UserDao

测试：

@Test
public void testAdd() throws Exception{
  BeanFactory ctx=new ClassPathXmlApplicationContext("beans.xml");
  
  UserService userService=(UserService)ctx.getBean("userService");
  System.out.println(userService.getUserDao());
}

结果:

daoid=1

也就是spring按照名字匹配上了<bean id="userDao"...那一项。(大概是按测试类里的UserDao类名来匹配的)

byType测试:

beans.xml中设置:

<?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-2.5.xsd">
  <bean id="userDao2" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="2"></property>
  </bean>
  
  <bean id="userService" class="cn.edu.hpu.service.UserService" autowire="byType">
  </bean>
  
</beans>

UserDaoImpl.java:

package cn.edu.hpu.dao.Impl;


import java.util.List;
import java.util.Map;
import java.util.Set;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserDaoImpl implements UserDao{


  private int daoId;
  
  
  public int getDaoId() {
    return daoId;
  }




  public void setDaoId(int daoId) {
    this.daoId = daoId;
  }




  public void save(User u) {
      System.out.println("add success!!");    
  }




  @Override
  public String toString() {
    
    return "daoid="+daoId;
  }
}

改写了toString方法，打印daoId，看看下面注入了哪个UserDao

测试：

@Test
public void testAdd() throws Exception{
  BeanFactory ctx=new ClassPathXmlApplicationContext("beans.xml");
  
  UserService userService=(UserService)ctx.getBean("userService");
  System.out.println(userService.getUserDao());
}

结果:

daoid=2

也就是spring按照类型匹配上了<bean id="userDao2"...那一项。(大概是按测试类里的UserDao类型匹配的)

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