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Spring DI依赖注入实战教程

2024-12-16 11:27:50 作者：你读书了吗？

这篇文章主要介绍了SpringDI依赖注入实战教程,本文通过实例代码给大家介绍的非常详细,需要的朋友可以参考下

1 概述

依赖
- A对象中有着B对象的引用，需要使用B对象完成一些操作
- A对象依赖B
注入
- 给A对象依赖的B对象赋值称为注入

2 注入方式

1、set注入

2、构造注入

3、自动注入

4、p命名空间注入

3 可以注入的数据类型

基本类型

自定义对象

容器类型

数组

集合

Map

Properties

4 set注入

创建对象的时候，Spring工厂会调用set方法给对象中的属性赋值
如果一个对象中的属性没有添加set方法，使用property赋值的时候偶会报错

Error:(11, 13) java: 找不到符号
  符号:   方法 setId(int)
  位置: 类型为com.sw.entity.User的变量 user

import lombok.Data;
@Data
public class User {
    private Integer id;
    private String username;
    private String password;
    private String addr;
    private String info;
}

<!--  定义user  -->
<bean id="user" class="com.sw.entity.User">
    <property name="id" value="100111"></property>
    <property name="username" value="关羽"></property>
    <property name="info" value="卖杂粮的关羽"></property>
</bean>

5 构造器注入

通过对象的构造器注入属性

<constructor-arg name="id" value="100110"></constructor-arg>

package com.sw.entity;
public class Hero {
    private Integer id;
    private String username;
    private String password;
    private String addr;
    private String info;
    public Hero() {
    }
    public Hero(String username, String password) {
        this.username = username;
        this.password = password;
    }
    public Hero(Integer id, String username) {
        this.id = id;
        this.username = username;
    }
    public Hero(Integer id, String username, String password, String addr, String info) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.addr = addr;
        this.info = info;
    }
    @Override
    public String toString() {
        return "Hero{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", addr='" + addr + '\'' +
                ", info='" + info + '\'' +
                '}';
    }
}

    <!--  定义Hero  -->
    <bean id="hero" class="com.sw.entity.Hero">
        <constructor-arg name="id" value="100110"></constructor-arg>
        <constructor-arg name="username" value="刘备"></constructor-arg>
    </bean>
    <bean id="hero02" class="com.sw.entity.Hero">
        <constructor-arg name="username" value="赵云"></constructor-arg>
        <constructor-arg name="password" value="zhao"></constructor-arg>
    </bean>

6 自动注入

在bean标签中声明autowire的方式

Spring框架会在容器中查找符合参数的数据进行注入

byType
byName

package com.sw.service.impl;
import com.sw.dao.HeroDao;
import com.sw.entity.Hero;
import com.sw.service.HeroService;
public class HeroServiceImpl implements HeroService {
    private HeroDao heroDao;
    public void setHeroDao(HeroDao heroDao) {
        this.heroDao = heroDao;
    }
    @Override
    public Hero queryHeroById(Integer id) {
        return heroDao.selectHeroById(id);
    }
}

    <!--  heroService  -->
    <bean id="heroService01" class="com.sw.service.impl.HeroServiceImpl" autowire="byType"></bean>
    <!--  heroService  -->
    <bean id="heroService02" class="com.sw.service.impl.HeroServiceImpl" autowire="byName"></bean>

    @Test
    public void getHero01(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        HeroService heroService = ioc.getBean("heroService01",HeroService.class);
        Hero hero = heroService.queryHeroById(10010);
        System.out.println(hero);
    }
    @Test
    public void getHero02(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        HeroService heroService = ioc.getBean("heroService02",HeroService.class);
        Hero hero = heroService.queryHeroById(1001111);
        System.out.println(hero);
    }

自动注入还是通过set注入的方式注入

7 p命名空间注入

使用p作为属性的前缀，调用属性执行复制的操作
实质上还是使用set方法赋值

xmlns:p=“http://www.springframework.org/schema/p”

    <!--  stu  -->
    <bean id="stu" class="com.sw.entity.Stu" p:id="100111" p:username="张三"></bean>

    @Test
    public void getStu(){
        ClassPathXmlApplicationContext ioc = 
        	new ClassPathXmlApplicationContext("applicationContext.xml");
        Stu stu = ioc.getBean(Stu.class);
        System.out.println(stu);
    }

8 数据源注入

使用Spring工厂注入Druid数据源
依赖

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.10</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>

在dao中声明数据源的引用

package com.sw.dao.impl;
import com.alibaba.druid.pool.DruidDataSource;
import com.sw.dao.HeroDao;
import com.sw.entity.Hero;
import java.sql.SQLException;
public class HeroDaoImpl implements HeroDao {
    private DruidDataSource dataSource;
    public DruidDataSource getDataSource() {
        return dataSource;
    }
    public void setDataSource(DruidDataSource dataSource) {
        this.dataSource = dataSource;
    }
    @Override
    public Hero selectHeroById(Integer id) {
        try {
            System.out.println(dataSource.getConnection());
        } catch (SQLException e) {
            e.printStackTrace();
        }
        Hero hero = new Hero();
        hero.setId(id);
        return hero;
    }
}

配置

      <!--  引入外部配置文件  -->
    <context:property-placeholder location="classpath:jdbc.properties"></context:property-placeholder>
  <!-- 配置数据源   -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"></property>
        <property name="url" value="${jdbc.url}"></property>
        <property name="username" value="${jdbc.username}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
    <!--  heroDao  -->
    <bean id="heroDao" class="com.sw.dao.impl.HeroDaoImpl">
        <property name="dataSource" ref="dataSource"></property>
    </bean>

测试

package com.sw;
import com.sw.dao.HeroDao;
import com.sw.entity.Hero;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.sql.SQLException;
public class TestHeroDao {
    @Test
    public void getHeroDao() {
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        HeroDao heroDao = ioc.getBean(HeroDao.class);
        Hero hero = heroDao.selectHeroById(222);
    }
}

4.9 容器类型数据注入

package com.sw.entity;
import lombok.Data;
import java.util.List;
import java.util.Map;
@Data
public class Person {
    private Integer id;
    private String username;
    private String gender;
    private String info;
    private String[] hobby;
    private List<String> friend;
    private Map<String,String> phones;
}

<?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:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       https://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       https://www.springframework.org/schema/context/spring-context.xsd">
    <!--  person基本属性注入  -->
    <bean id="person01" class="com.sw.entity.Person">
        <property name="id" value="100100"></property>
        <property name="username" value="宋江"></property>
        <property name="gender" value="male"></property>
        <property name="info" value="梁山头头"></property>
    </bean>
    <!--  注入数组  -->
    <bean id="person02" class="com.sw.entity.Person">
        <property name="hobby">
            <array>
                <value>篮球</value>
                <value>足球</value>
                <value>乒乓球</value>
            </array>
        </property>
    </bean>
    <bean id="person03" class="com.sw.entity.Person">
        <property name="friend">
            <list>
                <value>晁盖</value>
                <value>扈三娘</value>
                <value>王婆</value>
                <value>武松</value>
            </list>
        </property>
    </bean>
    <!--  map参数  -->
    <bean id="person04" class="com.sw.entity.Person">
        <property name="phones">
            <map>
                <entry key="鲁智深" value="10010"></entry>
                <entry key="林冲" value="10086"></entry>
                <entry key="李逵" value="10000"></entry>
                <entry key="李鬼" value="100000"></entry>
            </map>
        </property>
    </bean>
</beans>

package com.sw;
import com.sw.entity.Person;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class TestPerson {
    @Test
    public void getPerson01(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        Person person01 = ioc.getBean("person01", Person.class);
        System.out.println(person01);
    }
    @Test
    public void getPerson02(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        Person person02 = ioc.getBean("person02", Person.class);
        System.out.println(person02);
    }
    @Test
    public void getPerson03(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        Person person03 = ioc.getBean("person03", Person.class);
        System.out.println(person03);
    }
    @Test
    public void getPerson04(){
        ClassPathXmlApplicationContext ioc = new ClassPathXmlApplicationContext("applicationContext.xml");
        Person person04 = ioc.getBean("person04", Person.class);
        System.out.println(person04);
    }
}

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