• 依赖注入(六）

    文章目录

    文章目录

    一、setter注入

    • 依赖注入：Set注入
    • 依赖：bean对象的创建依赖于容器！
    • 注入：bean对象中的所有属性，由容器来注入！

    1.案例

    1.BookDao接口

    package com.study.dao;

public interface BookDao {
    void save();
}


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    2.BookDaoImpl实现类

    package com.study.dao.impl;

import com.study.dao.BookDao;

public class BookDaoImpl implements BookDao {
    public void save() {
        System.out.println("BookDaoImpl...");
    }
}



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    3.UserDao接口

    package com.study.dao;

public interface UserDao {
    void save();
}


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    4.UserServiceImpl实现类

    package com.study.dao.impl;

import com.study.dao.UserDao;

public class UserDaoImpl implements UserDao {
    private String name;
    private int age;
    public void save() {
        System.out.println(name+","+age);
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }
}


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    5.BookService接口

    package com.study.service;

public interface BookService {
    void save();
}


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    6.BookServiceImpl实现类

    package com.study.service.impl;

import com.study.dao.BookDao;
import com.study.dao.UserDao;
import com.study.service.BookService;

public class BookServiceImpl implements BookService {
    //简单类型
    private BookDao bookDao;
    private UserDao userDao;
    public void save() {
        bookDao.save();
        userDao.save();
        System.out.println("BookServiceImpl...");
    }

    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
}



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    7.applicationContext.xml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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="bookDao" class="com.study.dao.impl.BookDaoImpl"></bean>
    <bean id="UserDao" class="com.study.dao.impl.UserDaoImpl">
        <property name="name" value="小马哥"></property>
        <property name="age" value="34"></property>
    </bean>
    <bean id="bookService" class="com.study.service.impl.BookServiceImpl">
        <property name="bookDao" ref="bookDao"></property>
        <property name="userDao" ref="UserDao"></property>
    </bean>


</beans>

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    8.Test测试类

    import com.study.dao.BookDao;
import com.study.service.BookService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        BookService service = app.getBean(BookService.class);
        service.save();
    }
}
/*
BookDaoImpl...
小马哥,34
BookServiceImpl...
 */

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    二、构造器注入

    1. 使用无参构造创建对象，默认！
    2. 假设我们要使用有参构造创建对象。

    1.案例

    1.BookDao接口

    package com.study.dao;

public interface BookDao {
    void save();
}


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    2.BookDaoImpl实现类

    package com.study.dao.impl;

import com.study.dao.BookDao;

public class BookDaoImpl implements BookDao {
    public void save() {
        System.out.println("BookDaoImpl...");
    }
}




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    3.UserDao接口

    package com.study.dao;

public interface UserDao {
    void save();
}


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    4.UserServiceImpl实现类

    package com.study.dao.impl;

import com.study.dao.UserDao;

public class UserDaoImpl implements UserDao {
    private String name;
    private int age;
    public void save() {
        System.out.println(name+","+age);
    }

    public UserDaoImpl(String name, int age) {
        this.name = name;
        this.age = age;
    }
}


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    5.BookService接口

    package com.study.service;

public interface BookService {
    void save();
}


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    6.BookServiceImpl实现类

    package com.study.service.impl;

import com.study.dao.BookDao;
import com.study.dao.UserDao;
import com.study.dao.impl.BookDaoImpl;
import com.study.dao.impl.UserDaoImpl;
import com.study.service.BookService;

public class BookServiceImpl implements BookService {
    //简单类型
    private BookDao bookDao;
    private UserDao userDao;



    public void save() {
        bookDao.save();
        userDao.save();
        System.out.println("BookServiceImpl...");
    }

    public BookServiceImpl(BookDao bookDao, UserDao userDao) {
        this.bookDao = bookDao;
        this.userDao = userDao;
    }
}



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    7.applicationContext.xml配置文件

    注意：
    第一种方式：直接通过参数名来设置(推荐使用)
    第二种方式：下标赋值

    <?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="bookDao" class="com.study.dao.impl.BookDaoImpl"></bean>
    <bean id="UserDao" class="com.study.dao.impl.UserDaoImpl">
        <!--第一种方式：直接通过参数名来设置   -->
        <constructor-arg name="name" value="小马哥"/>
        <constructor-arg name="age" value="45"/>


        <!--第二种方式：下标赋值  -->
       <!-- <constructor-arg index="0" value="小马哥"/>
        <constructor-arg index="1" value="45"/>-->
    </bean>
    <bean id="bookService" class="com.study.service.impl.BookServiceImpl">
        <!--name是形参的值-->
        <constructor-arg name="bookDao" ref="bookDao"></constructor-arg>
        <constructor-arg name="userDao" ref="UserDao"></constructor-arg>
       
    </bean>


</beans>

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    8.Test测试类

    import com.study.dao.BookDao;
import com.study.service.BookService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        BookService service = app.getBean(BookService.class);
        service.save();
    }
}
/*
BookDaoImpl...
小马哥,45
BookServiceImpl...
 */

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    三、依赖注入方式选择

    在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/qq_43514330/article/details/125416080