package com.example.ba03;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("myStudent")
public class Student {
@Value(value = "张飞")
private String name;
@Value(value = "27")
private Integer age;
/*引用类型
* @Autowired:spring框架提供的注解,实现引用类型的赋值。
* spring中通过注解给引用类型赋值,使用的是自动注入原理,支持byName,byType
* @Autowired:默认使用的是byType自动注入
*
* 位置:1)在属性定义的上面,无需set方法,推荐使用
* 2)在set方法的上面
* */
@Autowired
private School school;
public void setName(String name) {
this.name = name;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", school=" + school +
'}';
}
}
package com.example.ba03;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("mySchool")
public class School {
@Value(value = "北京大学")
private String name;
@Value(value = "北京海淀区")
private String address;
public void setName(String name) {
this.name = name;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "School{" +
"name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="com.example.ba03"/>
<bean id="myXueXiao" class="com.example.ba03.School">
<property name="name" value="清华大学"/>
<property name="address" value="北京"/>
</bean>
</beans>
package com.example.ba04;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("myStudent")
public class Student {
@Value(value = "张飞")
private String name;
@Value(value = "27")
private Integer age;
/*引用类型
* @Autowired:spring框架提供的注解,实现引用类型的赋值。
* spring中通过注解给引用类型赋值,使用的是自动注入原理,支持byName,byType
* @Autowired:默认使用的是byType自动注入
*
* 位置:1)在属性定义的上面,无需set方法,推荐使用
* 2)在set方法的上面
*
* */
@Autowired
@Qualifier("mySchool")
private School school;
public void setName(String name) {
this.name = name;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", school=" + school +
'}';
}
}
package com.example.ba04;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("mySchool")
public class School {
@Value(value = "中山大学")
private String name;
@Value(value = "广州")
private String address;
public void setName(String name) {
this.name = name;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "School{" +
"name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
}
补充:当@Qualifier内的名称与引用类型中声明的@Component内的名称不同时,执行代码会出现这样的错误提示:
警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException:
Error creating bean with name 'myStudent': Unsatisfied dependency expressed through field 'school';
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:
No qualifying bean of type 'com.example.ba05.School' available:
expected at least 1 bean which qualifies as autowire candidate. Dependency annotations:
{@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=mySchool-01)}
这里Autowired(required=true)是Autowired的属性
属性:required,是boolean类型的,默认true
required=true:表示引用类型赋值失败,程序报错,并终止执行
required=fasle:表示引用类型赋值失败,程序正常执行,引用类型是null