spring学习总结009 --- 重复id或name的bean定义允许覆盖allowBeanDefinitionOverriding

默认情况下，单个配置文件中存在id或者name相同的bean定义，spring解析时会报错；不同配置文件中存在id或者name相同的bean定义，后面加载的bean定义会覆盖前面的bean定义

1、单个配置文件中存在id或者name相同的bean定义

<bean class="com.demo.bean.Info" id="myBean">
    <property name="age" value="28" />
</bean>

<bean class="com.demo.bean.User" id="myBean">
    <property name="id" value="1" />
    <property name="name" value="bale" />
</bean>

public class Test2 {
    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("classpath:spring/bean3.xml");
    }
}

运行结果：

Exception in thread "main" org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Bean name 'myBean' is already used in this <beans> element
Offending resource: class path resource [spring/bean3.xml]

    at org.springframework.beans.factory.parsing.FailFastProblemReporter.error(FailFastProblemReporter.java:72)
    at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:119)
    at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:111)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.error(BeanDefinitionParserDelegate.java:281)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.checkNameUniqueness(BeanDefinitionParserDelegate.java:488)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseBeanDefinitionElement(BeanDefinitionParserDelegate.java:434)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseBeanDefinitionElement(BeanDefinitionParserDelegate.java:405)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.processBeanDefinition(DefaultBeanDefinitionDocumentReader.java:306)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseDefaultElement(DefaultBeanDefinitionDocumentReader.java:197)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:176)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:149)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:96)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:511)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:338)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:310)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:188)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:224)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:195)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:257)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:128)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:94)
    at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:130)
    at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:638)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:523)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:144)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:85)
    at com.demo.test.Test2.main(Test2.java:7)

Process finished with exit code 1

报错源码：BeanDefinitionParserDelegate.checkNameUniqueness

2、不同配置文件中存在id或者name相同的bean定义

<bean id="myBean" class="com.demo.bean.User">
    <property name="id" value="1" />
    <property name="name" value="bale" />
</bean>

<bean id="myBean" class="com.demo.bean.Info">
    <property name="age" value="28" />
</bean>

@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private int id;
    private String name;
}

@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class Info {
    private int age;
}

public class Test1 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring/bean1.xml", "classpath:spring/bean2.xml");

        log.info("Bean: {}", context.getBean("myBean"));

        log.info("Info: {}", context.getBean(Info.class));

        log.info("User: {}", context.getBean(User.class));
    }
}

运行结果：

源码：DefaultListableBeanFactory.registerBeanDefinition

3、设置不允许重复bean定义覆盖

public class Test1 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring/bean1.xml", "classpath:spring/bean2.xml");

        context.setAllowBeanDefinitionOverriding(false);

        context.refresh();

        log.info("Bean: {}", context.getBean("myBean"));

        log.info("Info: {}", context.getBean(Info.class));

        log.info("User: {}", context.getBean(User.class));
    }
}

运行结果：

Exception in thread "main" org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Failed to register bean definition with name 'myBean'
Offending resource: class path resource [spring/bean2.xml]; nested exception is org.springframework.beans.factory.support.BeanDefinitionOverrideException: Invalid bean definition with name 'myBean' defined in class path resource [spring/bean2.xml]: Cannot register bean definition [Generic bean: class [com.demo.bean.Info]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [spring/bean2.xml]] for bean 'myBean': There is already [Generic bean: class [com.demo.bean.User]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [spring/bean1.xml]] bound.
    at org.springframework.beans.factory.parsing.FailFastProblemReporter.error(FailFastProblemReporter.java:72)
    at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:119)
    at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:104)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.processBeanDefinition(DefaultBeanDefinitionDocumentReader.java:314)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseDefaultElement(DefaultBeanDefinitionDocumentReader.java:197)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:176)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:149)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:96)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:511)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:338)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:310)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:188)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:224)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:195)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:257)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:128)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:94)
    at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:130)
    at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:638)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:523)
    at com.demo.test.Test1.main(Test1.java:15)
Caused by: org.springframework.beans.factory.support.BeanDefinitionOverrideException: Invalid bean definition with name 'myBean' defined in class path resource [spring/bean2.xml]: Cannot register bean definition [Generic bean: class [com.demo.bean.Info]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [spring/bean2.xml]] for bean 'myBean': There is already [Generic bean: class [com.demo.bean.User]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [spring/bean1.xml]] bound.
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.registerBeanDefinition(DefaultListableBeanFactory.java:941)
    at org.springframework.beans.factory.support.BeanDefinitionReaderUtils.registerBeanDefinition(BeanDefinitionReaderUtils.java:164)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.processBeanDefinition(DefaultBeanDefinitionDocumentReader.java:311)
    ... 18 more