Spring受管Bean依赖注入（设值注入）

柔光的暖阳◎ 2022-08-06 15:07 207阅读 0赞

设值注入是Spring支持的多种依赖注入类型中的一种，也是最为常见的一种。设值（setter）注入指在通过调用无参构造器（或无参静态工厂方法，或工厂Bean的蜚静态工厂方法）实例化受管Bean后调用setter方法，从而建立起对象之间的依赖关系。

一、无参构造器实例化受管Bean

public class HelloWorld implements IHelloWorld \{ protected static final Log log = LogFactory.getLog(HelloWorld.class); private IHelloStr helloStr; public HelloWorld() \{ super(); \} public void setHelloStr(IHelloStr str) \{ this.helloStr = str; \} public String getContent() \{ return helloStr.getContent(); \} \}

<?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 name="fileHello" class="test.FileHelloStrImpl"> <constructor-arg> <value>helloworld.properties</value> </constructor-arg> </bean> <bean id="helloWorld" class="test.HelloWorld"> <property name="helloStr" ref="fileHello" /> </bean> </beans>

我们可以通过ref属性指定依赖的对象或value属性直接给出目标对象。

二、无参静态工厂方法实例化受管Bean

如果希望通过调用无参静态工厂方法获得天受管Bean，则需要往对应的POJO类中添加静态方法以，以下为实例：

public class HelloWorld implements IHelloWorld \{ protected static final Log log = LogFactory.getLog(HelloWorld.class); private IHelloStr helloStr; public void setHelloStr(IHelloStr str) \{ this.helloStr = str; \} public String getContent() \{ return helloStr.getContent(); \} public static HelloWorld getHelloWorld()\{ return new HelloWorld(); \} \}

<?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="helloWorld" factory-method="getHelloWorld" class="test.HelloWorld"> <property name="helloStr" ref="fileHello"/> </bean> <bean name="fileHello" class="test.FileHelloStrImpl"> <constructor-arg> <value>helloworld.properties</value> </constructor-arg> </bean> </beans>

三、工厂Bean的非静态工厂方法实例受管Bean

同样的如果希望通过调用工厂Bean的非静态工厂方法获得受管Bean，则需要往对应的POJO类中添加非静态方法以，实例如下：

public class HelloWorld implements IHelloWorld \{ protected static final Log log = LogFactory.getLog(HelloWorld.class); private IHelloStr helloStr; public void setHelloStr(IHelloStr str) \{ this.helloStr = str; \} public String getContent() \{ return helloStr.getContent(); \} public HelloWorld makeHelloWorld()\{ return new HelloWorld(); \} \}

<?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="helloWorldFactory" class="test.HelloWorld"/> <bean id="helloWorld" factory-bean="helloWorldFactory" factory-method="makeHelloWorld"> <property name="helloStr" ref="fileHello"/> </bean> <bean name="fileHello" class="test.FileHelloStrImpl"> <constructor-arg> <value>helloworld.properties</value> </constructor-arg> </bean> </beans>

配置的helloWorldFactory受管Bean扮演了工厂Bean的角色。