If you perform the function of class A, B needs to participate in class, we believe that the dependent class B. Class A

2) Document Structure

Establishing a review process for CommentService class business, a DataService class is responsible for interaction with the database. Because the review is to retrieve data from the database, so CommentService class relies DataService class.

src

com.spring4

inter

ICommentService

public interface ICommentService {
    void getById(int id);
    void saveData(String str);
}

IDataService

public interface IDataService {
    String getById(int id);
    boolean saveComment(String str);
}

service

CommentService

public class CommentService implements ICommentService {
    public IDataService dataService = new DataService();

    CommentService public () {}

    @Override
    public void getById(int id){
        System.out.println(dataService.getById(id));
    }

    @Override 
    public void the saveData (String STR) { 
        Boolean In Flag = dataService.saveComment (STR); 
        IF (== In Flag to true) { 
            System.out.println ( "Comments saved successfully"); 
        } the else { 
            System.out.println ( "failed to save comment"); 
        } 
    } 
}

DataService

public class DataService implements IDataService {
    @Override
    public String  getById(int id){
        return  "这是第"+id+"条评论";
    }

    @Override
    public boolean saveComment(String str){
        return true;
    }
}

Application

public class Application {
    public static void main(String[] args) {
        ApplicationContext  applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        ICommentService commentService = (ICommentService) applicationContext.getBean("commentService");
        commentService.getById(22);
        commentService.saveData("JPA教程..");
    }
}

beans.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">
    <bean id="commentService" class="com.spring4.service.CommentService" >
    </bean>
</beans>

3）结果分析

运行输出结果为

我们使用到了DataService这个bean，但是我们在beans.xml文档中没有对这个bean进行配置。因此不能通过getBean(“标识”)来获取实例，所以我们通过new操作来获取这个bean的实例。

public class CommentService implements ICommentService {
    public IDataService dataService = new DataService();
    ...
}

Our function is indeed achieved, but it is not perfect, and therefore leads to the concept of dependency injection, see 7.【读】DI依赖注入.

Original: Big Box 6. dependencies [read]

6. dependencies [read]

2) Document Structure

3） 结果分析

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3）结果分析