【Spring实战】—— 8 自动装配

本篇介绍一下自动装配的知识,Spring为了简化配置文件的编写。采用自动装配方式,自动的装载需要的bean。

  自动装配 有以下几种方式:

  1 byName 通过id的名字与属性的名字进行判断,要保证Bean实例中属性名字与该装配的id名字相同。

  2 byType 通过类型确定装配的bean,但是当存在多个类型符合的bean时,会报错。

  3 contructor 在构造注入时,使用该装配方式,效果如同byType。

  4 autodetect 自动装配,这个测试了,3.0.5版本不可用了,不知道是不是被移除了。

 

  下面简单的看下,自动装配的所需代码:

public class Instrumentalist implements Performer{

    private String song;

    private int age;

    private Instrument instrument;

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getSong() {

        return song;

    }

    public void setSong(String song) {

        this.song = song;

    }

    public Instrument getInstrument() {

        return instrument;

    }

    public void setInstrument(Instrument instrument) {

        this.instrument = instrument;

    }

    public Instrumentalist(){}

    public Instrumentalist(String song,int age,Instrument instrument){

        this.song = song;

        this.age = age;

        this.instrument = instrument;

    }

    public void perform() throws PerformanceException {

        System.out.println("Instrumentalist age:"+age);

        System.out.print("Playing "+song+":");

        instrument.play();

    }

}
View Code
public interface Instrument {

    public void play();

}
View Code
public class Saxophone implements Instrument {

    public Saxophone(){}

    public void play() {

        System.out.println("TOOT TOOT TOOT");

    }

}
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public class test {

    public static void main(String[] args) throws PerformanceException {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml");

        

        Instrumentalist performer = (Instrumentalist)ctx.getBean("kenny");

        performer.perform();

        

    }

}
View Code

  采用byName方式的配置文件如下:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns="http://www.springframework.org/schema/beans"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    

    <bean id="instrument" class="com.spring.test.setter.Saxophone"/>

    <bean id="kenny" class="com.spring.test.setter.Instrumentalist" autowire="byName">

         <property name="song" value="Jingle Bells" />

         <property name="age" value="25" />

     </bean>

</beans>

  采用byType的配置文件如下:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns="http://www.springframework.org/schema/beans"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    

    <bean id="test2" class="com.spring.test.setter.Saxophone"/>

    <bean id="test1" class="com.spring.test.setter.Saxophone" primary="true"/> <!-- 默认是false -->

    <bean id="kenny" class="com.spring.test.setter.Instrumentalist" autowire="byType">

         <property name="song" value="Jingle Bells" />

         <property name="age" value="25" />

     </bean>

</beans>

  如果有多个类型匹配的bean,则可以采用 primary 来设置主要装配的bean,默认情况下是false

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