bean的两种传值方式

如果一个JavaBean类，封装了一些属性，有简单的数据类型，有引用类型，如何在配置文件中给这个Bean的对象进行传值呢？

方法有两种：
1.通过属性传值
2.通过构造方法传值
注意：

简单类型：用 name value
引用类型：用 name ref

Student和Phone的例子

Phone类：封装品牌和价格属性，重载构造器、getter/setter，覆写toString()方法

package com.spring;

public class Phone {
private String brand;
private double price;

public Phone(String brand, double price) {
    this.brand = brand;
    this.price = price;
}

public Phone() {
}

public String getBrand() {
    return brand;
}

public void setBrand(String brand) {
    this.brand = brand;
}

public double getPrice() {
    return price;
}

public void setPrice(double price) {
    this.price = price;
}

@Override
public String toString() {
    return "Phone{" +
            "brand='" + brand + '\'' +
            ", price=" + price +
            '}';
}

}

Student类：封装姓名、年龄、手机属性，其中手机属性为引用类型，重载构造器、getter/setter，覆写toString()方法

package com.spring;

public class Student {
private String name;
private int age;
private Phone phone;

public Student(String name, int age, Phone phone) {
    this.name = name;
    this.age = age;
    this.phone = phone;
}

public Student() {
}

public String getName() {
    return name;
}

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

public int getAge() {
    return age;
}

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

public Phone getPhone() {
    return phone;
}

public void setPhone(Phone phone) {
    this.phone = phone;
}

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

}

beans.xml配置文件,配置Phone的bean和Student的bean，用到了属性传值和构造器传值，并根据类型不同采用vaule和ref不同的方式。

<!--配置一个Phone类的bean，并采用构造器传值-->
<bean id="phone" class="com.spring.Phone">
    <constructor-arg name="brand" value="iPhoneX"/>
    <constructor-arg name="price" value="6888.88"/>
</bean>
<!--配置一个Student类的bean，并采用属性传值，注意ref的使用-->
<bean id="student" class="com.spring.Student">
    <property name="name" value="Tom"/>
    <property name="age" value="21"/>
    <property name="phone" ref="phone"/>
</bean>

编写主类进行测试

package com.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class StuentApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("/beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student);
}
}

运行结果，通过覆写toString()，打印对象，可以看到Student的对象中，引用了Phone的对象