正文
Spring -08 -自动注入 -byName/byType/constructor -全局使用default-autowire=” byName"
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1.在Spring 配置文件中对象名和ref=”id”id 名相同使用自动注入,可以不配置<property/>
2.两种配置办法
2.1在<bean>中通过 autowire=”” 配置,只对这个<bean>生效
2.2在<beans>中通过 default-autowire=””配置,表当当前文件中所有<bean>都是全局配置内容
3.autowire=”” 的可取值
3.1default: 默认值,根据全局 default-autowire=””值. 默认全局和局部都没有配置情况下,相当于no.
3.2no: 不自动注入
public class People { //类的关系
private Teacher teacher;
}
<bean id="teacher" class="com.test.Teacher"></bean>
<bean id="people" class="com.test.People" autowire="default">
<property name="teacher" ref="teacher"></property>
</bean>
<bean id="teacher" class="com.test.Teacher"></bean>
<bean id="people" class="com.test.People">
<property name="teacher" ref="teacher"></property>
</bean>
3.3byName: 通过名称自动注入.在Spring 容器中寻找缺省的类的同名的Id
<bean id="teacher" class="com.test.Teacher"></bean>
<bean id="people" class="com.test.People" autowire="byName"></bean>
3.4byType: 根据类型注入.
3.4.1spring 容器中不可以出现两个相同类型的<bean>
<bean id="teacher123" class="com.test.Teacher"></bean>
<bean id="people" class="com.test.People" autowire="byType"></bean>
输出: People{teacher=com.test.Teacher@6093dd95}
<bean id="teacher123" class="com.test.Teacher"></bean>
<bean id="teacher124" class="com.test.Teacher"></bean>
<bean id="people" class="com.test.People" autowire="byType"></bean>
输出报错信息:expected single matching bean but found 2: teacher123,teacher124
3.5constructor: 根据构造方法注入.
3.5.1提供对应参数的构造方法(构造方法参数中包含注入对戏那个)
<bean id="teacher123" class="com.test.Teacher"></bean>
<bean id="teacher" class="com.test.Teacher"></bean>
<!--保证constructor的入口参数和id的名称一致 -->
<bean id="people" class="com.test.People" autowire="constructor"></bean>
public class People {
private Teacher teacher; public People() {
} public People(Teacher teacher123) {
this.teacher = teacher123;
}
}
建议: 在全局使用default-autowire=” byName "
