Spring入門（二）——DI

• 2020 年 3 月 11 日
• 筆記

1. DI

Dependency Injection，依賴注入。當對象里有屬性或對象的時候，就需要為這些屬性或對象賦值

2. 流程

這裡介紹兩種方式

• set方法
• 註解方式

2.1 set方法

Bean準備

package bean;    import bean.Question;    public class User {        private String name;      private String email;      private String password;      private Question question;        /**      * 省略了getters/setters      * @author Howl      */        //set方法      public void setQuestion(Question question) {         this.question = question;      }        //構造函數      public User(String name, String email, String password) {          super();          this.name = name;          this.email = email;          this.password = password;      }  }

package bean;    import java.sql.Timestamp;  import java.util.Date;    public class Question {        private int id;      private Timestamp time;      private String content;        /**      * 省略了getters/setters      * @author Howl      */        //構造函數      public Question(int id, Timestamp time, String content) {          super();          this.id = id;          this.time = time;          this.content = content;      }  }

applictionContext.xml配置

<!--創建User對象-->  <bean id="User" class="User">      <!-- 依賴注入,setting自動注入 -->      <property name="Question" ref="Question"/>  </bean>     <!--創建Question對象-->  <bean id="Question" class="Question"></bean>

獲取對象

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");    //直接獲取  User user = ac.getBean("User");

2.2 註解方式

註解準備

package bean;    import bean.Question;    @Component  public class User {        private String name;      private String email;      private String password;      private Question question;        /**      * 省略了getters/setters      * @author Howl      */        //set方法      @Autowired      public void setQuestion(Question question) {         this.question = question;      }        //構造函數      public User(String name, String email, String password) {          super();          this.name = name;          this.email = email;          this.password = password;      }  }

獲取對象

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");    //直接獲取  User user = ac.getBean("User");