Spring框架03autowrite属性

1.创建需要的实体类

public class Student {   //学生实体类

    private  String   name;  //姓名
    private  Integer  age;  //年龄
    private  Grade   grade;  //年级
    
    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + ", grade=" + grade
                + "]";
    }
    
    public Student() {
        super();
    }
    public Student(String name, Integer age, Grade grade) {
        super();
        this.name = name;
        this.age = age;
        this.grade = grade;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public Grade getGrade() {
        return grade;
    }
    public void setGrade(Grade grade) {
        this.grade = grade;
    }
}

public class Grade {   //年级实体类
    private String  name;  //年级名称

    @Override
    public String toString() {
        return "Grade [name=" + name + "]";
    }

    public Grade() {
        super();
    }

    public Grade(String name) {
        super();
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

public class SmallGrade extends Grade {
  //只是为了 验证 autowire="byType"   
}

2.创建对应的配置文件

<?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:p="http://www.springframework.org/schema/p"  
    xmlns:c="http://www.springframework.org/schema/c"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean id="grade" class="cn.bdqn.bean.Grade" p:name="2年级"/>
  
  <!--autowire="byName" 将域属性名称 作为ID  到容器中查询相同名称的Bean进行注入  -->
   <bean id="student" class="cn.bdqn.bean.Student" autowire="byName"/>
   </beans>

 <?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:p="http://www.springframework.org/schema/p"  
    xmlns:c="http://www.springframework.org/schema/c"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean id="gradeaaaaa" class="cn.bdqn.bean.Grade" p:name="2年级"/>
     <!-- autowire="byType" 根据域属性的类型 到容器中查询 相同类型并且具有is-a关系的一个Bean进行注入
   相同类型的bean不能多于一个   -->
    <bean id="student" class="cn.bdqn.bean.Student" autowire="byType"/>
    
</beans>

3.创建测试类分类运行

public class StudentTest {
    
    @Test
    public  void  test01(){
        ApplicationContext context=
                new ClassPathXmlApplicationContext("applicationContext.xml");
         Student student=(Student) context.getBean("student");
        System.out.println(student);
    }
}

4.如果在autowire="byType" 的时候 在容器中在增加一个相同类型的bean或者有is-a的关系    会报错！ 

如下的代码  运行会报错 

<?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:p="http://www.springframework.org/schema/p"  
    xmlns:c="http://www.springframework.org/schema/c"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean id="gradeaaa" class="cn.bdqn.bean.Grade" p:name="2年级"/>
  <bean id="smallgrade" class="cn.bdqn.bean.SmallGrade"/>
   <!-- autowire="byType" 根据域属性的类型 到容器中查询 相同类型并且具有is-a关系的一个Bean进行注入
   相同类型的bean不能多于一个   -->
    <bean id="student" class="cn.bdqn.bean.Student" autowire="byType"/>
    
</beans>

<?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:p="http://www.springframework.org/schema/p"  
    xmlns:c="http://www.springframework.org/schema/c"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean id="grade1" class="cn.bdqn.bean.Grade" p:name="1年级"/>
  <bean id="grade2" class="cn.bdqn.bean.Grade" p:name="2年级"/>

   
   <!-- autowire="byType" 根据域属性的类型 到容器中查询 相同类型并且具有is-a关系的一个Bean进行注入
   相同类型的bean不能多于一个   -->
    <bean id="student" class="cn.bdqn.bean.Student" autowire="byType"/>
    
</beans>