Spring系列：基于XML的方式构建IOC

一、搭建模块spring6-ioc-xml
二、获取bean的三种方式
三、基于setter注入
四、基于构造器注入
五、特殊值处理
六、为对象类型属性赋值
七、引入外部属性文件
八、基于XML自动装配

一、搭建模块spring6-ioc-xml

①引入配置文件

引入spring6-ioc-xml模块配置文件：beans.xml、log4j2.xml


<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="user" class="com.mcode.bean.User"/>
beans>

②添加依赖

<dependencies>
       
       
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-contextartifactId>
            <version>6.0.13version>
        dependency>
       
        <dependency>
            <groupId>org.junit.jupitergroupId>
            <artifactId>junit-jupiter-apiartifactId>
            <version>5.9.3version>
        dependency>
       
        <dependency>
            <groupId>org.apache.logging.log4jgroupId>
            <artifactId>log4j-coreartifactId>
            <version>2.20.0version>
        dependency>
        <dependency>
            <groupId>org.apache.logging.log4jgroupId>
            <artifactId>log4j-slf4j2-implartifactId>
            <version>2.20.0version>
        dependency>
    dependencies>

③引入java类

引入spring6-ioc-xml模块java及test目录下实体类

package com.mcode.bean;

/**
 * ClassName: User
 * Package: com.mcode.bean
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 10:33 PM
 * @Version: v1.0
 */
public class User {
    public User() {
        System.out.println("无参数构造方法执行");
    }

    public void test(){
        System.out.println("test...");
    }
}

package com.mcode;

import com.mcode.bean.Student;
import com.mcode.bean.User;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * ClassName: UserTest
 * Package: com.mcode
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 10:34 PM
 * @Version: v1.0
 */
public class UserTest {
    private Logger logger = LoggerFactory.getLogger(UserTest.class);

    @Test
    public void testUser(){
    }
}

二、获取bean的三种方式

①方式一：根据id获取

由于 id 属性指定了 bean 的唯一标识，所以根据 bean 标签的 id 属性可以精确获取到一个组件对象。

    @Test
    public void testUser(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User) applicationContext.getBean("user");
        user.test();
    }

②方式二：根据类型获取

    @Test
    public void testUser1(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User) applicationContext.getBean(User.class);
        user.test();
    }

③方式三：根据id和类型

    @Test
    public void testUser2(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User) applicationContext.getBean("user",User.class);
        user.test();
    }

④注意的地方

当根据类型获取bean时，要求IOC容器中指定类型的bean有且只能有一个

当IOC容器中一共配置了两个：

    <bean id="user" class="com.mcode.bean.User"/>
    <bean id="user2" class="com.mcode.bean.User"/>

根据类型获取时会抛出异常：

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'com.mcode.bean.User' available: expected single matching bean but found 2: user,user2

三、基于setter注入

①创建学生类Student

package com.mcode.bean;

/**
 * ClassName: Student
 * Package: com.mcode.bean
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 10:46 PM
 * @Version: v1.0
 */
public class Student {
    private Integer id;
    private String  name;
    private Integer age;
    private String sex;

    public Student() {
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

②配置bean时为属性赋值

spring-di.xml

<bean id="studentOne" class="com.mcode.bean.Student">
    
    
    
     <property name="id" value="1">property>
     <property name="name" value="robin">property>
     <property name="age" value="18">property>
     <property name="sex" value="男">property>
bean>

③测试

    @Test
    public void testDIBySet(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-di.xml");
        Student student = applicationContext.getBean("studentOne", Student.class);
        System.out.println(student);
    }

四、基于构造器注入

①在Student类中添加有参构造

public Student(Integer id, String name, Integer age, String sex) {
    this.id = id;
    this.name = name;
    this.age = age;
    this.sex = sex;
}

②配置bean

spring-di.xml

    <bean id="studentTwo" class="com.mcode.bean.Student">
        <constructor-arg value="1">constructor-arg>
        <constructor-arg value="robin">constructor-arg>
        <constructor-arg value="20">constructor-arg>
        <constructor-arg value="男">constructor-arg>
    bean>

注意：

constructor-arg标签还有两个属性可以进一步描述构造器参数：

index属性：指定参数所在位置的索引（从0开始）

name属性：指定参数名

③测试

    @Test
    public void testDIByConstructor(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-di.xml");
        Student student = applicationContext.getBean("studentTwo", Student.class);
        System.out.println(student);
    }

五、特殊值处理

①字面量赋值

什么是字面量？

int a = 10;

声明一个变量a，初始化为10，此时a就不代表字母a了，而是作为一个变量的名字。当我们引用a的时候，我们实际上拿到的值是10。

而如果a是带引号的：'a'，那么它现在不是一个变量，它就是代表a这个字母本身，这就是字面量。所以字面量没有引申含义，就是我们看到的这个数据本身。


<property name="name" value="张三"/>

②null值

<property name="name">
    <null />
property>

注意：
<property name="name" value="null">property>
以上写法，为name所赋的值是字符串null

③xml实体



<property name="expression" value="a < b"/>

④CDATA节

<property name="expression">
    
    
    
    
    <value>value>
property>

六、为对象类型属性赋值

①创建班级类Clazz

package com.mcode.bean;

/**
 * ClassName: Clazz
 * Package: com.mcode.bean
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 10:53 PM
 * @Version: v1.0
 */
public class Clazz {
    private Integer clazzId;
    private String clazzName;

    public Clazz() {
    }

    public Clazz(Integer clazzId, String clazzName) {
        this.clazzId = clazzId;
        this.clazzName = clazzName;
    }

    @Override
    public String toString() {
        return "Clazz{" +
                "clazzId=" + clazzId +
                ", clazzName='" + clazzName + '\'' +
                '}';
    }

    public Integer getClazzId() {
        return clazzId;
    }

    public void setClazzId(Integer clazzId) {
        this.clazzId = clazzId;
    }

    public String getClazzName() {
        return clazzName;
    }

    public void setClazzName(String clazzName) {
        this.clazzName = clazzName;
    }
}

②修改Student类

在Student类中添加以下代码：

private Clazz clazz;

public Clazz getClazz() {
	return clazz;
}

public void setClazz(Clazz clazz) {
	this.clazz = clazz;
}

方式一：引用外部bean

配置Clazz类型的bean：

<bean id="clazzOne" class="com.mcode.bean.Clazz">
    <property name="clazzId" value="1111">property>
    <property name="clazzName" value="财源滚滚班">property>
bean>

为Student中的clazz属性赋值：

<bean id="studentFour" class="com.mcode.bean.Student">
    <property name="id" value="1004">property>
    <property name="name" value="赵六">property>
    <property name="age" value="26">property>
    <property name="sex" value="女">property>
    
    <property name="clazz" ref="clazzOne">property>
bean>

方式二：内部bean

<bean id="studentFour" class="com.mcode.bean.Student">
    <property name="id" value="1004">property>
    <property name="name" value="赵六">property>
    <property name="age" value="26">property>
    <property name="sex" value="女">property>
    <property name="clazz">
        
        
        <bean id="clazzInner" class="com.mcode.bean.Clazz">
            <property name="clazzId" value="2222">property>
            <property name="clazzName" value="远大前程班">property>
        bean>
    property>
bean>

方式三：级联属性赋值

<bean id="studentFour" class="com.mcode.bean.Student">
    <property name="id" value="1004">property>
    <property name="name" value="赵六">property>
    <property name="age" value="26">property>
    <property name="sex" value="女">property>
    <property name="clazz" ref="clazzOne">property>
    <property name="clazz.clazzId" value="3333">property>
    <property name="clazz.clazzName" value="最强王者班">property>
bean>

七、引入外部属性文件

①加入依赖

 
<dependency>
    <groupId>mysqlgroupId>
    <artifactId>mysql-connector-javaartifactId>
    <version>8.0.30version>
dependency>


<dependency>
    <groupId>com.alibabagroupId>
    <artifactId>druidartifactId>
    <version>1.2.15version>
dependency>

②创建外部属性文件

jdbc.user=root
jdbc.password=123456
jdbc.url=jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC
jdbc.driver=com.mysql.cj.jdbc.Driver

③引入属性文件

引入context 名称空间


<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">

beans>


<context:property-placeholder location="classpath:jdbc.properties"/>

注意：在使用 context:property-placeholder 元素加载外包配置文件功能前，首先需要在 XML 配置的一级标签中添加 context 相关的约束。

④配置bean

<bean id="druidDataSource" class="com.alibaba.druid.pool.DruidDataSource">
    <property name="url" value="${jdbc.url}"/>
    <property name="driverClassName" value="${jdbc.driver}"/>
    <property name="username" value="${jdbc.user}"/>
    <property name="password" value="${jdbc.password}"/>
bean>

⑤测试

@Test
public void testDataSource() throws SQLException {
    ApplicationContext ac = new ClassPathXmlApplicationContext("spring-datasource.xml");
    DataSource dataSource = ac.getBean(DataSource.class);
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
}

八、基于XML自动装配

自动装配：

根据指定的策略，在IOC容器中匹配某一个bean，自动为指定的bean中所依赖的类类型或接口类型属性赋值

①场景模拟

创建类UserController

package com.mcode.autowire.controller;

import com.mcode.autowire.service.UserService;

/**
 * ClassName: UserController
 * Package: com.mcode.autowire.controller
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 11:29 PM
 * @Version: v1.0
 */
public class UserController {
    private UserService userService;


    public void setUserService(UserService userService) {
        this.userService = userService;
    }

    public void getUser(){
        userService.getUser();
    }

}

创建接口UserService

package com.mcode.autowire.service;

/**
 * ClassName: UserService
 * Package: com.mcode.autowite.service
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 11:30 PM
 * @Version: v1.0
 */
public interface UserService {
    void getUser();
}

创建类UserServiceImpl实现接口UserService

package com.mcode.autowire.service.impl;

import com.mcode.autowire.service.UserService;

/**
 * ClassName: UserServiceImpl
 * Package: com.mcode.autowire.service.impl
 * Description:
 *
 * @Author: robin
 * @Create: 2023/11/7 - 11:31 PM
 * @Version: v1.0
 */
public class UserServiceImpl implements UserService {
    @Override
    public void getUser() {
        System.out.println("获取user...");
    }
}

②配置bean

使用bean标签的autowire属性设置自动装配效果

自动装配方式：byType

byType：根据类型匹配IOC容器中的某个兼容类型的bean，为属性自动赋值

若在IOC中，没有任何一个兼容类型的bean能够为属性赋值，则该属性不装配，即值为默认值null

若在IOC中，有多个兼容类型的bean能够为属性赋值，则抛出异常NoUniqueBeanDefinitionException


<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="userService" class="com.mcode.autowire.service.impl.UserServiceImpl"/>

    <bean id="userController" class="com.mcode.autowire.controller.UserController" autowire="byType"/>

beans>

自动装配方式：byName

byName：将自动装配的属性的属性名，作为bean的id在IOC容器中匹配相对应的bean进行赋值


<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="userService" class="com.mcode.autowire.service.impl.UserServiceImpl"/>
    <bean id="userController" class="com.mcode.autowire.controller.UserController" autowire="byName"/>

beans>

③测试

    @Test
    public void testAutoWireByXML(){
        ApplicationContext ac = new ClassPathXmlApplicationContext("spring-autowire.xml");
        UserController userController = ac.getBean(UserController.class);
        userController.getUser();
    }

相关阅读:
Android基础-AndroidManifest.xml详解
 网络观察方法
 LeetCode每日一题(2310. Sum of Numbers With Units Digit K)
HTML学生个人网站作业设计——中华美食(HTML+CSS) 美食静态网页制作 WEB前端美食网站设计与实现
 DolphinScheduler 1.x使用经验篇及bug解决篇
 git常用命令
 程序员的孤独你不懂
 07、vue : 无法加载文件 C:\Users\JH\AppData\Roaming\npm\vue.ps1，因为在此系统上禁止运行脚本。
Java多线程-将全量用户表70万数据压缩并生成CSV文件和推送到FTP上(最快方式-10秒)
Linux--安装部署Docker
原文地址：https://www.cnblogs.com/vic-tory/p/17816381.html