02Spring基于xml的IOC配置--实例化Bean的三种方…

2019-11-15 16:05:45来源：博客园阅读 ()

02Spring基于xml的IOC配置--实例化Bean的三种方式

maven依赖

    <dependencies>
        <!--IOC相关依赖-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.0.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

applicationContext.xml

<?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">



</beans>

1、使用默认无参构造函数实例化bean

1.1 创建Student实体类

public class Student {
    private String name;
    private Integer age;

    
    public void say() {
        System.out.println("I'm a Student");
    }

    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;
    }
}

1.2 在applicationContext.xml文件中装配Student对象

<?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">


    <!-- 装配Studnt对象到IOC容器中 -->
    <bean id="student" class="com.demo.domain.Student"/>

</beans>

1.3 测试

    private ApplicationContext ac;

    @Before
    public void init() {
        //加载配置文件
        ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    }


    @Test
    public void getStudentObjectFromSrpingIoc() {
        //1. 根据bean的id去IOC容器中获取Student对象
        Student student = (Student) ac.getBean("student");
        //2. say
        student.say();
    }

2. 使用静态工厂方法实例化bean

2.1 创建Teacher实体类

public class Teacher {

    public void say() {
        System.out.println("I'm a teacher");
    }
}

2.2 创建静态工厂类

public class StaticFactory {

    /**
     * 用于创建Teacher对象
     * @return
     */
    public static Teacher createTeacher() {
        return new Teacher();
    }
}

2.3 使用静态工厂方法装配Teacher对象

<?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">

    <!-- 装配Studnt对象到IOC容器中 -->
    <bean id="student" class="com.demo.domain.Student"/>

    <!-- 使用静态工厂方法将Teacher对象装配到IOC容器中 -->
    <bean id="teacher" class="com.demo.factory.StaticFactory" factory-method="createTeacher"/>


</beans>

2.4 测试

    @Test
    public void getTeaccherObjectFromSrpingIoc() {
        //1. 根据bean的id去IOC容器中获取Teacher对象
        Teacher teacher = (Teacher) ac.getBean("teacher");
        //2. say
        teacher.say();
    }

3、使用实例工厂方法实例化bean

3.1 创建Cat实体类

public class Cat {
    public void say() {
        System.out.println("I'm a cat");
    }
}

3.2 创建实例工厂类

public class InstanceFactory {

    /**
     * 用于创建cat对象
     * @return
     */
    public Cat createCat() {
        return new Cat();
    }
}

3.3 使用实例工厂创建Cat对象

<?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">


    <!-- 装配Studnt对象到IOC容器中 -->
    <bean id="student" class="com.demo.domain.Student"/>

    <!-- 使用静态工厂方法将Teacher对象装配到IOC容器中 -->
    <bean id="teacher" class="com.demo.factory.StaticFactory" factory-method="createTeacher"/>

    <!-- 使用实例工厂方法实例化bean -->
    <!-- 1. 装配实例工厂-->
    <bean id="instanceFactory" class="com.demo.factory.InstanceFactory"/>
    <!-- 2. 使用实例工厂创建cat对象-->
    <bean id="cat" factory-bean="instanceFactory" factory-method="createCat"/>

</beans>

3.4 测试

    @Test
    public void getCatObjectFromSrpingIoc() {
        //1. 根据bean的id去IOC容器中获取Cat对象
        Cat cat = (Cat) ac.getBean("cat");
        //2. say
        cat.say();
    }