Spring入门——DI

Posted 2020-11-24 Howlet

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1. DI

Dependency Injection，依赖注入。当对象里有属性或对象的时候，就需要为这些属性或对象赋值

2. 流程

这里介绍两种方式

• set方法
• 注解方式

2.1 set方法

Bean准备

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;
    }
    
    //构造函数
    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
    */
    
    //构造函数
    public Question(int id, Timestamp time, String content) {
        super();
        this.id = id;
        this.time = time;
        this.content = content;
    }
}

applictionContext.xml配置

<!--创建User对象-->
<bean id="User" class="User">
    <!-- 依赖注入,setting自动注入 -->
    <property name="Question" ref="Question"/>
</bean>

 <!--创建Question对象-->
<bean id="Question" class="Question"></bean>

获取对象

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

//直接获取
User user = ac.getBean("User");

2.2 注解方式

注解准备

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;
    }
    
    //构造函数
    public User(String name, String email, String password) {
        super();
        this.name = name;
        this.email = email;
        this.password = password;
    }
}

获取对象

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

//直接获取
User user = ac.getBean("User");