Spring的IOC以及Bean管理

我就是我 2023-01-15 03:49 134阅读 0赞

下面主要讲一下Bean管理即赋值的三种方法（设值注入，构造注入和自动装配）

项目结构如下图

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70][]

## 实体类Student ##

package com.gxy.entity;/**
     * Created by 86157 on 2021/4/19.
     */
    
    /**
     * @author 86157
     * @version 1.0
     * @description: TODO
     * @date 2021/4/19 15:45
     */
    public class Student {
        private int sno;
        private String sname;
        private int age;
        private char gender;
        private Teacher teacher;
    
        public Student(int sno, String sname, int age, char gender, Teacher teacher) {
            this.sno = sno;
            this.sname = sname;
            this.age = age;
            this.gender = gender;
            this.teacher = teacher;
        }
    
        public int getSno() {
            return sno;
        }
    
        public void setSno(int sno) {
            this.sno = sno;
        }
    
        public String getSname() {
            return sname;
        }
    
        public void setSname(String sname) {
            this.sname = sname;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        public char getGender() {
            return gender;
        }
    
        public void setGender(char gender) {
            this.gender = gender;
        }
    
        public Teacher getTeacher() {
            return teacher;
        }
    
        public void setTeacher(Teacher teacher) {
            this.teacher = teacher;
        }
    
        @Override
        public String toString() {
            return "Student{" +
                    "sno=" + sno +
                    ", sname='" + sname + '\'' +
                    ", age=" + age +
                    ", gender=" + gender +
                    ", teacher=" + teacher +
                    '}';
        }
    
        public Student() {
            super();
        }
    }

## 实体类Teacher ##

package com.gxy.entity;/**
     * Created by 86157 on 2021/4/20.
     */
    
    /**
     * @author 86157
     * @version 1.0
     * @description: TODO
     * @date 2021/4/20 15:42
     */
    public class Teacher {
        private int tid;
        private String tname;
        private String tprofession;
    
        public Teacher(int tid, String tname, String tprofession) {
            this.tid = tid;
            this.tname = tname;
            this.tprofession = tprofession;
        }
    
        public int getTid() {
            return tid;
        }
    
        public void setTid(int tid) {
            this.tid = tid;
        }
    
        public String getTname() {
            return tname;
        }
    
        public void setTname(String tname) {
            this.tname = tname;
        }
    
        public String getTprofession() {
            return tprofession;
        }
    
        public void setTprofession(String tprofession) {
            this.tprofession = tprofession;
        }
    
        @Override
        public String toString() {
            return "Teacher{" +
                    "tid=" + tid +
                    ", tname='" + tname + '\'' +
                    ", tprofession='" + tprofession + '\'' +
                    '}';
        }
    
        public Teacher() {
            super();
        }
    }

## 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-3.2.xsd">
    
         <bean id="user" class="com.gxy.entity.Student">
             <!–设值注入  setter  name与对应实体类中set方法名一致–>
               <property name="sno" value="1907272110"/>
               <property name="sname" value="王秘书"/>
               <property name="age" value="20"/>
               <property name="gender" value="女"/>
               <property name="teacher" ref="teacher"/>
           </bean>
           <bean id="teacher" class="com.gxy.entity.Teacher">
               <property name="tname" value="王老师"/>
               <property name="tid" value="007"/>
               <property name="tprofession" value="国际抬杠教练"/>
           </bean>
            
        <bean id="user" class="com.gxy.entity.Student">
        <constructor-arg value="1907272110"/>
            <constructor-arg value="王秘书"/>
            <constructor-arg value="20"/>
            <constructor-arg value="女"/>
            <constructor-arg ref="teacher"/>
        </bean>
        <bean id="teacher" class="com.gxy.entity.Teacher">
            <constructor-arg>
                <value>3001</value>
            </constructor-arg>
            <constructor-arg>
                <value>刘世忠</value>
            </constructor-arg>
            <constructor-arg>
                <value>摄影</value>
            </constructor-arg>
        </bean>
        
        
        <bean id="autostu" class="com.gxy.entity.Student" autowire="byName">
            <property name="sno" value="1907272110"/>
            <property name="sname" value="王秘书"/>
            <property name="age" value="20"/>
            <property name="gender" value="女"/>
        </bean>
        <bean id="teacher" class="com.gxy.entity.Teacher" >
            <property name="tid" value="3001"></property>
            <property name="tname" value="王老师"></property>
            <property name="tprofession" value="地理"></property>
        </bean>
    </beans>

## 测试类： ##

package com.gxy.test;/**
     * Created by 86157 on 2021/4/19.
     */
    
    import com.gxy.entity.Student;
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * @author 86157
     * @version 1.0
     * @description: TODO
     * @date 2021/4/19 15:47
     */
    public class Test_01 {
        @Test
        public void method() {
            //spring是一个轻量级Ioc和AOP的容器框架    解决类与类之间的解耦合
            // 加载spring配置文件，创建工厂
            ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
            //根据配置文件中的bean id,获取对象
            Student stu = (Student) context.getBean("autostu");
            //输出
            System.out.println("stu = " + stu);
        }
    }

## Spring，IOC概念： ##

spring是一个轻量级Ioc和AOP的容器框架    用来解决类与类之间的解耦合  降低企业开发的复杂性

IoC是Inversion of Control的缩写，有的翻译成“控制反转”，还有翻译成为“控制反向”或者“控制倒置”。

个人理解IOC就是对象原来是由程序员创建的，现在交给Spring去处理，但是你要告诉他怎么来创建。

bean就是由IOC容器初始化，装配及管理的对象。

## Bean装配： ##

接下来主要描述三种方法即设值注入，构造注入和自动装配

### Bean装配之设值注入： ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 1][]

bean标签中id为标识符，随后会在applicationcontext获取对象时用到，property标签用来给对象赋值，name为实体类中属性名，对于对象类型，使用ref引入，ref通过唯一标识符来查找对象

测试类运行结果如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 2][]

底层实现目前看不出来，现在在实体类中setter，getter，构造方法中加入提示，如下：

![20210421154424748.png][]

![20210421154432729.png][]

现在再来运行下看看结果

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 3][]

从上面我们可以看出来运行后，读取配置文件首先创建了对象，然后调用setter方法进行赋值，由此我们可以得出结论

设值注入底层实现：setter

### Bean装配之构造注入： ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 4][]

使用构造注入时，不需要写类中属性名，但是需要按照有参方法中的参数顺序进行依次赋值，否则报错如：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 6][]

会提示转换值时候报错，也就是说你这个类中类型和你赋值的类型不一致，转化失败，现在正常运行下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 7][]

构造注入底层实现：构造方法

### Bean装配之自动装配： ###

TIP:DI 给对象类型赋值  自动装配，不能自动装配所谓简单类型例如基本类型，字符串和集合类

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 8][]

autowire属性即自动装配，属性有以下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 9][]

这里演示byname即通过名字，通过实体类中对象类型的名字进行装配

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 10][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 11][]

运行如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ExMDQ0NzczMjA3_size_16_color_FFFFFF_t_70 12][]

自动装配底层实现：setter

### 总结到此为止，如有错误，欢迎多多指教 ###

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[20210421154424748.png]: /images/20221022/f26521ad0e52412bb2d5bbd5f1c9f09a.png
[20210421154432729.png]: /images/20221022/2f416010de3c41cea4b875ae1094d2df.png
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