Spring 集合注入與建構子注入實戰：List、Set、Map、Properties 完整配置範例

業務介面定義

public interface IPersonService {
    void save();
    Set<String> getSets();
    List<String> getLists();
    Properties getProperties();
    Map<String, String> getMaps();
}

實作類別

public class PersonServiceBean implements IPersonService {
    private IPersonDao personDao;
    private String name; // 建構子注入
    
    // 集合屬性
    private Set<String> sets = new HashSet<>();
    private List<String> lists = new ArrayList<>();
    private Properties properties = new Properties();
    private Map<String, String> maps = new HashMap<>();

    // 建構子注入：Dao + name
    public PersonServiceBean(IPersonDao personDao, String name) {
        this.personDao = personDao;
        this.name = name;
    }

    // Getter/Setter 略...
    
    public void save() {
        System.out.println(name); // 輸出建構子注入的 name
        personDao.add();
    }
}

Spring XML 配置

<beans xmlns="https://www.springframework.org/schema/beans"
       xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="https://www.springframework.org/schema/beans
       https://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

  <!-- 目標 Bean -->
  <bean id="personService" class="cn.itcast.service.impl.PersonServiceBean">
    <!-- 建構子注入：index 0=Dao, index 1=String -->
    <constructor-arg index="0" ref="personDaoBean" type="cn.itcast.dao.IPersonDao"/>
    <constructor-arg index="1" type="java.lang.String" value="傳智博客"/>

    <!-- 集合屬性注入 -->
    <property name="sets">
        <set>
            <value>set1</value>
            <value>set2</value>
            <value>set3</value>
        </set>
    </property>

    <property name="lists">
        <list>
            <value>list1</value>
            <value>list2</value>
            <value>list3</value>
        </list>
    </property>

    <property name="properties">
        <props>
            <prop key="properties1">property1</prop>
            <prop key="properties2">property2</prop>
            <prop key="properties3">property3</prop>
        </props>
    </property>

    <property name="maps">
        <map>
            <entry key="key1" value="keyFirst"/>
            <entry key="key2" value="keySecond"/>
            <entry key="key3" value="keyThird"/>
        </map>
    </property>
  </bean>

  <bean id="personDaoBean" class="cn.itcast.dao.impl.PersonDaoBean"/>
</beans>

測試驗證

@Test
public void testInjection() {
    ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
    IPersonService service = (IPersonService) ctx.getBean("personService");

    // 遍歷輸出
    System.out.println("=== Set ===");
    service.getSets().forEach(System.out::println);
    
    System.out.println("=== List ===");
    service.getLists().forEach(System.out::println);
    
    System.out.println("=== Properties ===");
    service.getProperties().keySet().forEach(System.out::println);
    
    System.out.println("=== Map ===");
    service.getMaps().keySet().forEach(System.out::println);

    service.save(); // 輸出: 傳智博客 + Dao 邏輯
}

執行結果

=== Set ===
set1
set2
set3
=== List ===
list1
list2
list3
=== Properties ===
properties3
properties2
properties1
=== Map ===
key1
key2
key3
傳智博客
這是 personDaoBean 的 Add() 方法

關鍵點總結

• 建構子注入適合**強制依賴**（不可變物件、線程安全）
• Setter 注入適合**可選依賴**
• ref 參考其他 Bean，value 直接字面值
• 複雜集合可巢狀：<list><ref bean="..."/></list>