### 屬性 ``` type: 要注入的數據的數據類型 index: 注入的數據在構造函數中的所以位置，從0開始 name: 參數 value: 值 ref: 用于指定其他的bean類型數據 ``` ### 優缺點 ``` 1. 獲取對象，必須注入數據，或者對象無法創建成功 2. 創建對象時，如果用不到，也必須提供 ``` ### bean ~~~ public class UserService { private String name; private Integer age; private Date birthday; public UserService(String name, Integer age, Date birthday) { this.name = name; this.age = age; this.birthday = birthday; } public void saveUser(){ System.out.println(name + " --- "+ age + " --- "+ birthday); } } ~~~ ### bean.xml ~~~ <bean id="userService" class="com.test.service.UserService"> <constructor-arg name="name" value="test"/> <constructor-arg name="age" value="11"/> <constructor-arg name="birthday" ref="now"/> </bean> <!--配置一個日期對象--> <bean id="now" class="java.util.Date"/> ~~~ ### test ~~~ public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml"); UserService userService = (UserService) ac.getBean("userService"); userService.saveUser(); } ~~~