Spring中的构造注入

public class School {
    private String name;
    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 + '\'' +
                '}';
    }
}

public class Student {
    private String name;
    private int age;
    private School school;

    public Student() {
        System.out.println("Student的无参构造方法");
    }

    public Student(String myName, int myAge, School mySchool){
        System.out.println("Student的有参构造方法");
        this.name = myName;
        this.age = myAge;
        this.school = mySchool;
    }

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

    public void setAge(int age) {
        this.age = age;
    }

    public void setSchool(School school) {
        this.school = school;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", school=" + school +
                '}';
    }
}

<!--
    构造注入使用<constructor-arg>标签
    一个<constructor-arg>标签表示构造方法的一个参数
    <constructor-arg>标签属性：
        name：表示构造方法的形参名
        index：表示构造方法中参数的位置，自左向右从0开始
           value：构造方法的形参类型是简单类型，使用value
        ref：构造方法的形参类型是引用类型，使用ref
        
    下面分别使用name和index来完成构造注入
-->
<!--使用name属性-->
<bean id="myStudent1" class="com.xxx.package01.Student">
    <constructor-arg name="myName" value="张三" />
    <constructor-arg name="myAge" value="20" />
    <constructor-arg name="mySchool" ref="mySchool" />
</bean>
<!--使用index属性-->
<bean id="myStudent2" class="com.xxx.package01.Student">
    <constructor-arg index="0" value="张三" />
    <constructor-arg index="1" value="20" />
    <constructor-arg index="2" ref="mySchool" />
</bean>

<bean id="mySchool" class="com.xxx.package01.School">
    <property name="name" value="北京大学" />
    <property name="address" value="北京" />
</bean>

public class MyTest {
    @Test
    public void test01(){
        String config = "package01/applicationContext.xml";
        ApplicationContext ac = new ClassPathXmlApplicationContext(config);

        //使用myStudent1或myStudent2对象都能完成注入
        Student myStudent = (Student) ac.getBean("myStudent1");
        //Student myStudent = (Student) ac.getBean("myStudent2");
        System.out.println("Student = " + myStudent);
    }
}