Spring框架构造注入

Spring框架实现注入的方法有很多种，其一，构造注入

典型的三层架构：

package dao;

import entity.User;

/**
 * 增加DAO接口,定义了所需的持久化方法
 */
public interface UserDao {
    public void save(User user);
}

package dao.impl;

import dao.UserDao;
import entity.User;

/**
 * 用户DAO类，实现IDao接口，负责User类的持久化操作
 */
public class UserDaoImpl implements UserDao {

    public void save(User user) {
        // 这里并未实现完整的数据库操作，仅为说明问题
        System.out.println("保存用户信息到数据库");
    }
}

package service;

import entity.User;

/**
 * 用户业务接口，定义了所需的业务方法
 */
public interface UserService {
    public void addNewUser(User user);
}

package service.impl;

import service.UserService;
import dao.UserDao;
import entity.User;

/**
 * 用户业务类，实现对User功能的业务管理
 */
public class UserServiceImpl implements UserService {

    // 声明接口类型的引用，和具体实现类解耦合
    private UserDao dao;

    // 生成无参构造方法
    public UserServiceImpl() {

    }

    // 带参数构造方法   为dao进行赋值
    public UserServiceImpl(UserDao dao) {
        this.dao = dao;
    }

    public UserDao getDao() {
        return dao;
    }

    // dao 属性的setter访问器，会被Spring调用，实现设值注入
    public void setDao(UserDao dao) {
        this.dao = dao;
    }

    public void addNewUser(User user) {
        // 调用用户DAO的方法保存用户信息
        dao.save(user);
    }
}

实体类：

package entity;

/**
 * 用户实体类
 */
public class User implements java.io.Serializable {
    private Integer id; // 用户ID
    private String username; // 用户名
    private String password; // 密码
    private String email; // 电子邮件

    // getter & setter
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

}

核心配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">
    <!--以上是Spring框架的头信息 -->
    <!--放置要被管理的对象实例 -->
    <!-- 使用构造注入的方式 -->
    <bean id="userDao" class="dao.impl.UserDaoImpl"></bean>
    <bean id="UserService" class="service.impl.UserServiceImpl">
        <!--通过构造函数的方式，实现构造注入 -->
        <constructor-arg>
            <ref bean="userDao" />
        </constructor-arg>
    </bean>

</beans>

测试方法：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import service.UserService;
import service.impl.UserServiceImpl;

import entity.User;


public class AopTest {

    @Test
    public void aopTest() {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = (UserService) ctx.getBean("UserService");
        
        User user = new User();
        user.setId(1);
        user.setUsername("test");
        user.setPassword("123456");
        user.setEmail("test@xxx.com");

        service.addNewUser(user);
    }

}

运行结果：

12-29 16:22:52[INFO]org.springframework.context.support.ClassPathXmlApplicationContext
 -Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2db0f6b2: startup date [Sun Dec 29 16:22:52 CST 2019]; root of context hierarchy
12-29 16:22:52[INFO]org.springframework.beans.factory.xml.XmlBeanDefinitionReader
 -Loading XML bean definitions from class path resource [applicationContext.xml]
12-29 16:22:52[INFO]org.springframework.beans.factory.support.DefaultListableBeanFactory
 -Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@2f686d1f: defining beans [userDao,UserService]; root of factory hierarchy
保存用户信息到数据库