1、获取bean对象的三种基本方式

0、前提准备

<?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">
    <!--使用spring创建对象
    id:名称一般采用类名的首字母小写
    class：要创建对象的全限定类名
    property：属性
    name：对象的属性名称
    value：想要赋值的值
    创建完成之后会将其存放在ioc容器中
    -->
    <bean id="person" class="cn.simplelife.domain.Person">
        <property name="id" value="1"/>
        <property name="name" value="李四"/>
    </bean>
</beans>

1、按照名称查找

ApplicationContext context = new ClassPathXmlApplicationContext("bean的配置文件名称") 
context.getBean("person")

注意：返回值是Object需要强转为我们需要的类型。

2、按照类型查找

ApplicationContext context = new ClassPathXmlApplicationContext("bean的配置文件名称") 
context.getBean(Person.class)

注意：如果在xml中配置了多个该类型的对象，就会报错。

3、按照名称和类型查找

ApplicationContext context = new ClassPathXmlApplicationContext("bean的配置文件名称") 
context.getBean("person",Person.class)

2、常见异常

1、org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named ‘person’ available

【错误示例】：
在这里插入图片描述
【错误原因】： 此时的错误是告诉我们在spring框架中没有叫做person的bean对象，也就是我们在xml配置中没有配置该对象。

【解决方案】： 在配置文件中配置该名称的bean对象。

2、No qualifying bean of type ‘cn.simplelife.domain.Person’ available: expected single matching bean but found 2: person,person1

【错误提示】：

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'cn.simplelife.domain.Person' available: expected single matching bean but found 2: person,person1

	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:1036)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:338)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:333)
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1107)
	at PersonTest.testPersonBySpring(PersonTest.java:32)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)