Spring中的工厂bean

1.普通bean与工厂bean

Spring 有两种类型 bean，一种普通 bean，另外一种工厂 bean(FactoryBean)

• 普通 bean:在配置文件中定义 bean 类型就是返回类型
• 工厂 bean:在配置文件定义 bean 类型可以和返回类型不一样

2.工厂bean的步骤

1. 创建类，让这个类作为工厂 bean，实现接口 FactoryBean

public class MyFactoryBean implements FactoryBean<Student> {
    

    //定义返回 bean
    @Override
    public Student getObject() throws Exception {
    
        Student student = new Student();
        student.setName("工厂bean");
        return student;
    }

    @Override
    public Class<?> getObjectType() {
    
        return null;
    }

    @Override
    public boolean isSingleton() {
    
        return false;
    }
}

    //定义返回 bean
    @Override
    public Student getObject() throws Exception {
     
        Student student = new Student();
        student.setName("工厂bean");
        return student;
    }

代码示例：
Student类：

public class Student {
      
    private String name;
    private int age;
    private String gender;

    public Student() {
      
    }

    public Student(String name, int age, String gender) {
      

        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    public String getName() {
      
        return name;
    }

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

    public int getAge() {
      
        return age;
    }

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

    public String getGender() {
      
        return gender;
    }

    public void setGender(String gender) {
      
        this.gender = gender;
    }

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

xml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.xsd">
    <bean id="myFactoryBean" class="iocbean.byxml.factorybean.MyFactoryBean">

    </bean>
</beans>

测试类：

public class TestDemo {
        
    @Test
    public void test(){
        
        ApplicationContext context = new ClassPathXmlApplicationContext("iocbean/byxml/factorybean/bean.xml");

        Student bean = context.getBean("myFactoryBean", Student.class);

        System.out.println(bean);
    }
}

输出结果：

Student{name='工厂bean', age=0, gender='null'} Process finished with exit code 0