Spring框架——IOC 容器的创建与使用

企业级开发框架　　

　　Spring Framework 是整个 Spring 生态的基础，各个模块都是基于 Spring Framework 衍生出来的。

　　Spring 的两大核心机制 IOC 控制翻转、AOP 面向切面编程。

　　　　IOC 对象创建不再由开发者完成，而是容器自动创建，开发者直接取出来用即可。

1、新建maven项目

2、添加依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.sunjian</groupId>
    <artifactId>springPrac</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.2.RELEASE</version>
        </dependency>
    </dependencies>

</project>

3、新建实体类

Student

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/14 9:13
 */
public class Student {
    private String id;

    public String getId() {
        return id;
    }

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

    private String name;
    private String age;

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

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

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

Student2

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/14 10:05
 */
public class Student2 {
    private String id;
    private String name;
    private String age;

    public Student2(String id, String name, String age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public String getId() {
        return id;
    }

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

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

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

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

Student3

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/14 10:05
 */
public class Student3 {
    private String id;
    private String name;
    private String age;
    private Student4 student4;

    public Student4 getStudent4() {
        return student4;
    }

    public void setStudent4(Student4 student4) {
        this.student4 = student4;
    }

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Student3{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", age='" + age + '\'' +
                ", student4=" + student4 +
                '}';
    }
}

Student4

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/14 10:05
 */
public class Student4 {
    private String id;
    private String name;
    private String age;

    public String getId() {
        return id;
    }

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

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

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

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

Students

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/14 12:05
 */
public class Students {
    private String id;
    private String name;
    private String age;
    private Classes classes;

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

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

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

    public Classes getClasses() {
        return classes;
    }

    public void setClasses(Classes classes) {
        this.classes = classes;
    }
}

Classes

package com.sunjian.entity;

import java.util.List;

/**
 * @author sunjian
 * @date 2020/3/14 12:02
 */
public class Classes {
    private String id;
    private String name;
    private List<Students> students;

    public List<Students> getStudents() {
        return students;
    }

    public void setStudents(List<Students> students) {
        this.students = students;
    }

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Classes{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", students=" + students +
                '}';
    }
}

4、在resources目录下新建spring.xml文件，添加bean

<?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">

    <!-- 无参构造方式 -->
    <bean id="stu" class="com.sunjian.entity.Student">
        <property name="id" value="1"></property>
        <!--<property name="name" value="sunjian"></property>-->
        <!--特殊字符处理-->
        <property name="name">
            <value>
                <![CDATA[<孙健>]]>
            </value>
        </property>
        <property name="age" value="32"></property>
    </bean>

    <!-- 有参构造方式 1-->
    <bean id="stu_1" class="com.sunjian.entity.Student2">
        <constructor-arg index="0" value="1"></constructor-arg>
        <constructor-arg index="1" value="孙健"></constructor-arg>
        <constructor-arg index="2" value="31"></constructor-arg>
    </bean>
    <!-- 有参构造方式 2 常用 -->
    <bean id="stu_2" class="com.sunjian.entity.Student2">
        <constructor-arg name="id" value="1"></constructor-arg>
        <constructor-arg name="name" value="孙健"></constructor-arg>
        <constructor-arg name="age" value="32"></constructor-arg>
    </bean>
    <!-- 有参构造方式 3-->
    <bean id="stu_3" class="com.sunjian.entity.Student2">
        <constructor-arg value="1"></constructor-arg>
        <constructor-arg value="孙健"></constructor-arg>
        <constructor-arg value="33"></constructor-arg>
    </bean>

    <!-- 两个bean的级联方式 一对一-->
    <bean id="stu3" class="com.sunjian.entity.Student3">
        <property name="id" value="1"></property>
        <property name="age" value="33"></property>
        <property name="name" value="sunjian stu3"></property>
        <property name="student4" ref="stu4"></property>
    </bean>
    <bean id="stu4" class="com.sunjian.entity.Student4">
        <property name="id" value="1"></property>
        <property name="age" value="34"></property>
        <property name="name" value="sunjian stu4"></property>
    </bean>

    <!-- bean对象之间的集合注入 一对多-->
    <bean id="classes" class="com.sunjian.entity.Classes">
        <property name="id" value="1"></property>
        <property name="name" value="243班"></property>
        <property name="students">
            <list>
                <ref bean="stus1"></ref>
                <ref bean="stus2"></ref>
                <ref bean="stus3"></ref>
            </list>
        </property>
    </bean>
    <bean id="stus1" class="com.sunjian.entity.Students">
        <property name="id" value="1"></property>
        <property name="name" value="张三"></property>
        <property name="age" value="30"></property>
    </bean>
    <bean id="stus2" class="com.sunjian.entity.Students">
        <property name="id" value="2"></property>
        <property name="name" value="李四"></property>
        <property name="age" value="31"></property>
    </bean>
    <bean id="stus3" class="com.sunjian.entity.Students">
        <property name="id" value="3"></property>
        <property name="name" value="赵四"></property>
        <property name="age" value="32"></property>
    </bean>

</beans>

5、测试类

package com.sunjian.test;

import com.sunjian.entity.*;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author sunjian
 * @date 2020/3/14 9:14
 */
public class Test {
    public static void main(String[] args) {
        // 加载IOC容器
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");

        System.out.println("-------------无参构造方式-------------------------");

        // 根据bean的id去拿
//        Student student = (Student) applicationContext.getBean("stu");
        // 根据类型去拿 （注意：spring.xml中只能有一个class="com.sunjian.entity.Student"）
        Student student = applicationContext.getBean(Student.class);
        System.out.println(student);

        System.out.println("-------------有参构造方式-------------------------");

//        Student2 student2 = (Student2) applicationContext.getBean("stu_2");
//        Student2 student2 = (Student2) applicationContext.getBean("stu_3");
        Student2 student2 = (Student2) applicationContext.getBean("stu_1");
        System.out.println(student2);

        System.out.println("--------------两个bean的级联方式------------------------");

        Student3 student3 = (Student3) applicationContext.getBean("stu3");
        System.out.println(student3);

        System.out.println("---------------bean对象之间的集合注入-----------------------");
        Classes classes = (Classes) applicationContext.getBean("classes");
        System.out.println(classes);
    }
}

运行结果

-------------无参构造方式-------------------------
Student{id='1', name='
                <孙健>
            ', age='32'}
-------------有参构造方式-------------------------
Student{id='1', name='孙健', age='31'}
--------------两个bean的级联方式------------------------
Student3{id='1', name='sunjian stu3', age='33', student4=Student{id='1', name='sunjian stu4', age='34'}}
---------------bean对象之间的集合注入-----------------------
Classes{id='1', name='243班', students=[Students{id='1', name='张三', age='30'}, Students{id='2', name='李四', age='31'}, Students{id='3', name='赵四', age='32'}]}

6、注意事项

• 实体类中，必须有无参构造。
• 成员变量必须有setter方法。

　　IOC实例化对象的过程，通过反射 + XML解析的方式对spring.xml进行处理，反射拿到无参构造函数，调用创建对象，同时获取setter方法，调用完成成员变量的赋值。

OK.