Spring入门（5）-自动装配Bean属性

本文介绍如何装配Bean属性。

0. 目录

ByName
ByType
constructor
默认自动装配
混合使用自动装配和显示装配

1. ByName

把与Bean的属性具有相同名字（或ID）的其他Bean自动装配到Bean对应的属性中。如果没有跟属性名称相匹配的Bean，则该属性不进行装配。

package com.chzhao.springtest;

public class PersonBll implements IPersonBll {

	private Person person;

	public Person getPerson() {
		return person;
	}

	public void setPerson(Person person) {
		this.person = person;
	}

	public void show() {
		System.out.println(this.person.getName());
	}
}

<?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 name="person" class="com.chzhao.springtest.Person">
		<property name="name" value="老王" />
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll" autowire="byName">
	</bean> 
</beans>

2. ByType

把与Bean的属性具有相同类型的其他Bean自动装配到Bean对应的属性中。如果没有跟属性类型相匹配的Bean，则该属性不进行装配。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 	
	http://www.springframework.org/schema/beans/spring-beans.xsd">
	<bean name="laowang" class="com.chzhao.springtest.Person">
		<property name="name" value="老王" />
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll" autowire="byType">
	</bean> 
</beans>

如上，如果设置为byType，Bean的名字随便设置了，不需要为person

3. constructor

把与Bean的构造器入参具有相同类型的其他Bean自动装配到Bean构造器的对应入参中。

package com.chzhao.springtest;

public class PersonBll implements IPersonBll {

	public PersonBll(Person person) {
		this.person = person;
	}

	private Person person;

	public void show() {
		System.out.println(this.person.getName());
	}
}

<?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 name="laowang" class="com.chzhao.springtest.Person">
		<property name="name" value ="老王"></property>
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll" autowire="constructor">
	</bean> 
</beans>

4. 默认自动装配

Spring可以通过设置default-autowire使所有Bean采取相同配置。

<?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.xsd"
	default-autowire="constructor">
	<bean name="laowang" class="com.chzhao.springtest.Person">
		<property name="name" value ="老王"></property>
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll">
	</bean> 
</beans>

5. 混合使用自动装配和显示装配

即使对某个Bean的属性采用了自动装配，仍然可以通过显示装配配置某个属性。

package com.chzhao.springtest;

public class PersonBll implements IPersonBll {

	public Person getPerson() {
		return person;
	}

	public void setPerson(Person person) {
		this.person = person;
	}

	private Person person;

	public void show() {
		System.out.println(this.person.getName());
	}
}

<?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"
	default-autowire="byType"
	>
	<bean name="laowang" class="com.chzhao.springtest.Person">
		<property name="name" value="老王" />
	</bean>
	<bean name="laoli" class="com.chzhao.springtest.Person">
		<property name="name" value="老李" />
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll" >
		<property name="person" ref="laoli"></property>
	</bean> 
</beans>