default-autowire使用

Posted 2021-03-19 vvii

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共五种值可供选择，属于全局的设置

• 复用的BeanA类

public class BeanA {
    private BeanB beanB;
    private BeanC beanC;

    public BeanB getBeanB() {
        return beanB;
    }

    public BeanA setBeanB(BeanB beanB) {
        this.beanB = beanB;
        return this;
    }

    public BeanC getBeanC() {
        return beanC;
    }

    public BeanA setBeanC(BeanC beanC) {
        this.beanC = beanC;
        return this;
    }
}

• 复用的Test 类

import com.vi.springbean.BeanA;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;

public class Test {
    @org.junit.Test
    public void test() {
        String path = "spring-config.xml";
        BeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource(path));

        BeanA bean = beanFactory.getBean(BeanA.class);

        System.out.println("beanB  "+bean.getBeanB());
        System.out.println("beanC  "+bean.getBeanC());
    }
}

default-autowire="byType"

• 情况1

<?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 id="beanA" class="com.vi.springbean.BeanA"></bean>
    <bean id="beanBB" class="com.vi.springbean.BeanB"></bean>
    <bean id="beanC" class="com.vi.springbean.BeanD"></bean>
</beans>

运行结果：
beanB com.vi.springbean.BeanB@568bf312
beanC null

• 情况2

<?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 id="beanA" class="com.vi.springbean.BeanA"></bean>
    <bean id="beanBB"  class="com.vi.springbean.BeanB"></bean>
    <bean id="beanCC" class="com.vi.springbean.BeanB"></bean>
</beans>

• 运行结果：
  org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name ‘beanA‘ defined in class path resource [spring-config.xml]: Unsatisfied dependency expressed through bean property ‘beanB‘; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type ‘com.vi.springbean.BeanB‘ available: expected single matching bean but found 2: beanBB,beanCC

说明可以找不到，但是不能存在多个类型一样的，匹配时与bean的id无关

default-autowire="byName"

• 情况1

<?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="byName">


    <bean id="beanA" class="com.vi.springbean.BeanA"></bean>
    <bean id="beanB" class="com.vi.springbean.BeanB"></bean>
    <bean id="beanC2" class="com.vi.springbean.BeanB"></bean>
</beans>

运行结果：
beanB com.vi.springbean.BeanB@5d47c63f
beanC null

可以找不到，且可以存在多个同类型的

• 情况2

<?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="byName">


    <bean id="beanA" class="com.vi.springbean.BeanA"></bean>
    <bean id="beanB" class="com.vi.springbean.BeanB"></bean>
    <bean id="beanC" class="com.vi.springbean.BeanD"></bean>
</beans>

运行结果：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘beanA‘ defined in class path resource [spring-config.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type ‘com.vi.springbean.BeanD‘ to required type ‘com.vi.springbean.BeanC‘ for property ‘beanC‘; nested exception is java.lang.IllegalStateException: Cannot convert value of type ‘com.vi.springbean.BeanD‘ to required type ‘com.vi.springbean.BeanC‘ for property ‘beanC‘: no matching editors or conversion strategy found
说明当通过name匹配到后，类型不能不符也是错误的

• 情况3

<?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="byName">


<bean id="beanA" class="com.vi.springbean.BeanA"></bean>
<bean id="beanB" class="com.vi.springbean.BeanB"></bean>
<bean id="beanB" class="com.vi.springbean.BeanC"></bean>

</beans>

运行结果：
org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Bean name ‘beanB‘ is already used in this element
Offending resource: class path resource [spring-config.xml]

此时按照name去匹配的，bean的id和BeanA的中的属性 name一致即可注入，可以找不到，找到之后类型需要一致，xml中bean id的值需保证唯一性

default-autowire="constructor"

// TODO

default-autowire="default"

// TODO

default-autowire="no"

// TODO