跟老杜手撕Spring6教程（十一）set注入专题-2

级联属性赋值（了解）

本篇文章说说set注入专题之级联属性赋值，上篇说了set注入专题

​​https://blog.51cto.com/u_15485663/6132751​​

配合视频教程观看，更易理解吸收，动力节点老杜的Spring6教程采用难度逐步递进的方式，从入门的第一个程序到手写Spring框架，真正的能够让小白成为老手。如果你是老程序员不妨看看手写Spring框架，也会让你受益颇多。

package com.powernode.spring6.beans;

/**
 * @author 动力节点
 * @version 1.0
 * @className Clazz
 * @since 1.0
 **/
public class Clazz {
    private String name;

    public Clazz() {
    }

    public Clazz(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Clazz{" +
                "name='" + name + '\'' +
                '}';
    }
}
package com.powernode.spring6.beans;

/**
 * @author 动力节点
 * @version 1.0
 * @className Student
 * @since 1.0
 **/
public class Student {
    private String name;
    private Clazz clazz;

    public Student() {
    }

    public Student(String name, Clazz clazz) {
        this.name = name;
        this.clazz = clazz;
    }

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

    public void setClazz(Clazz clazz) {
        this.clazz = clazz;
    }

    public Clazz getClazz() {
        return clazz;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", clazz=" + clazz +
                '}';
    }
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="clazzBean" class="com.powernode.spring6.beans.Clazz"/>

    <bean id="student" class="com.powernode.spring6.beans.Student">
        <property name="name" value="张三"/>

        <!--要点1：以下两行配置的顺序不能颠倒-->
        <property name="clazz" ref="clazzBean"/>
        <!--要点2：clazz属性必须有getter方法-->
        <property name="clazz.name" value="高三一班"/>
    </bean>
</beans>
@Test
public void testCascade(){
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-cascade.xml");
    Student student = applicationContext.getBean("student", Student.class);
    System.out.println(student);
}

运行结果：

要点：

• 在spring配置文件中，如上，注意顺序。
• 在spring配置文件中，clazz属性必须提供getter方法。

注入数组

当数组中的元素是简单类型：

package com.powernode.spring6.beans;

import java.util.Arrays;

public class Person {
    private String[] favariteFoods;

    public void setFavariteFoods(String[] favariteFoods) {
        this.favariteFoods = favariteFoods;
    }

    @Override
    public String toString() {
        return "Person{" +
                "favariteFoods=" + Arrays.toString(favariteFoods) +
                '}';
    }
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="person" class="com.powernode.spring6.beans.Person">
        <property name="favariteFoods">
            <array>
                <value>鸡排</value>
                <value>汉堡</value>
                <value>鹅肝</value>
            </array>
        </property>
    </bean>
</beans>
@Test
public void testArraySimple(){
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-array-simple.xml");
    Person person = applicationContext.getBean("person", Person.class);
    System.out.println(person);
}

当数组中的元素是非简单类型：一个订单中包含多个商品。

package com.powernode.spring6.beans;

/**
 * @author 动力节点
 * @version 1.0
 * @className Goods
 * @since 1.0
 **/
public class Goods {
    private String name;

    public Goods() {
    }

    public Goods(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Goods{" +
                "name='" + name + '\'' +
                '}';
    }
}
package com.powernode.spring6.beans;

import java.util.Arrays;

/**
 * @author 动力节点
 * @version 1.0
 * @className Order
 * @since 1.0
 **/
public class Order {
    // 一个订单中有多个商品
    private Goods[] goods;

    public Order() {
    }

    public Order(Goods[] goods) {
        this.goods = goods;
    }

    public void setGoods(Goods[] goods) {
        this.goods = goods;
    }

    @Override
    public String toString() {
        return "Order{" +
                "goods=" + Arrays.toString(goods) +
                '}';
    }
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="goods1" class="com.powernode.spring6.beans.Goods">
        <property name="name" value="西瓜"/>
    </bean>

    <bean id="goods2" class="com.powernode.spring6.beans.Goods">
        <property name="name" value="苹果"/>
    </bean>

    <bean id="order" class="com.powernode.spring6.beans.Order">
        <property name="goods">
            <array>
                <!--这里使用ref标签即可-->
                <ref bean="goods1"/>
                <ref bean="goods2"/>
            </array>
        </property>
    </bean>

</beans>

测试程序：

@Test
public void testArray(){
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-array.xml");
    Order order = applicationContext.getBean("order", Order.class);
    System.out.println(order);
}

执行结果：

要点：

• 如果数组中是简单类型，使用value标签。
• 如果数组中是非简单类型，使用ref标签。

注入List集合

List集合：有序可重复

package com.powernode.spring6.beans;

import java.util.List;

/**
 * @author 动力节点
 * @version 1.0
 * @className People
 * @since 1.0
 **/
public class People {
    // 一个人有多个名字
    private List<String> names;

    public void setNames(List<String> names) {
        this.names = names;
    }

    @Override
    public String toString() {
        return "People{" +
                "names=" + names +
                '}';
    }
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="peopleBean" class="com.powernode.spring6.beans.People">
        <property name="names">
            <list>
                <value>铁锤</value>
                <value>张三</value>
                <value>张三</value>
                <value>张三</value>
                <value>狼</value>
            </list>
        </property>
    </bean>
</beans>
@Test
public void testCollection(){
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-collection.xml");
    People peopleBean = applicationContext.getBean("peopleBean", People.class);
    System.out.println(peopleBean);
}

执行结果：

注意：注入List集合的时候使用list标签，如果List集合中是简单类型使用value标签，反之使用ref标签。