在 Spring 中注入 List, Set, Map，我们该怎么进行注入呢？，这篇文章接下来讲的 就是这个。 如果你对注入不太了解的话，可以看这篇文章。
Spring 依赖注入（基础）

List

首先我们要有个 Student 类

public class Student {

    private String name;

    private int age;

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

    public void study() {
        System.out.println(name + "在学习");
    }

    public String getName() {
        return name;
    }
}

接下来是管理 Student 类的 School 类

public class School {

    private List<Student> studentList;

    public School(List<Student> studentList) {
        this.studentList = studentList;
    }

    public void study() {
        for (Student student : studentList) {
            student.study();
        }
    }

}

接下来是 bean.xml

<?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">

    <beans>
        <bean id="school" class="com.draper.School">
            <constructor-arg>
                <list>
                    <bean id="stu1" class="com.draper.Student">
                        <constructor-arg index="0">
                            <value>小俊</value>
                        </constructor-arg>
                        <constructor-arg index="1">
                            <value>14</value>
                        </constructor-arg>
                    </bean>
                    
                    <bean id="stu2" class="com.draper.Student">
                        <constructor-arg index="0">
                            <value>小贝</value>
                        </constructor-arg>
                        <constructor-arg index="1">
                            <value>14</value>
                        </constructor-arg>
                    </bean>
                </list>
            </constructor-arg>
        </bean>
    </beans>

</beans>

亦或是应用我们上篇文章学的 在 bean 中注入 bean

<?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">

    <beans>
        <bean id="stu1" class="com.draper.Student">
            <constructor-arg index="0">
                <value>小俊</value>
            </constructor-arg>
            <constructor-arg index="1">
                <value>14</value>
            </constructor-arg>
        </bean>
        <bean id="stu2" class="com.draper.Student">
            <constructor-arg index="0">
                <value>小贝</value>
            </constructor-arg>
            <constructor-arg index="1">
                <value>14</value>
            </constructor-arg>
        </bean>
        <bean id="school" class="com.draper.School">
            <constructor-arg>
                <list>
                    <ref bean="stu1"/>
                    <ref bean="stu2"/>
                </list>
            </constructor-arg>
        </bean>
    </beans>

</beans>

对比我们前面学的总结下
<list> 的标签其实他已经给你封装好了，<set>, <map>也是一样，只不过细节上有些不同， 而引入另外一个 bean 还是用了 <ref>
让我们来测试一下

public class TestApp {

    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
        School school = (School) context.getBean("school");
        school.study();
    }
}

Set

Set 就是把标签换成 <set>，再修改下类就可以了

Map

为了方便演示，略微修改 Student 类

public class School {

    private Map<String, Student> studentMap;

    public School(Map<String, Student> studentMap) {
        this.studentMap = studentMap;
    }

    public void study(){
        Set<String> keySet = studentMap.keySet();
        for (String s : keySet) {
            studentMap.get(s).study();
        }
    }

}

修改 bean.xml

<?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">

    <beans>
        <bean id="stu1" class="com.draper.Student">
            <constructor-arg index="0">
                <value>小俊</value>
            </constructor-arg>
            <constructor-arg index="1">
                <value>14</value>
            </constructor-arg>
        </bean>
        <bean id="stu2" class="com.draper.Student">
            <constructor-arg index="0">
                <value>小贝</value>
            </constructor-arg>
            <constructor-arg index="1">
                <value>14</value>
            </constructor-arg>
        </bean>
        <bean id="school" class="com.draper.School">
            <constructor-arg>
                <map>
                    <entry key="stu1">
                        <ref bean="stu1"/>
                    </entry>
                    <entry key="stu2">
                        <ref bean="stu2"/>
                    </entry>
                </map>
            </constructor-arg>
        </bean>
    </beans>

</beans>

测试代码没有改动

的确有点神奇哈