Spring实例化对象的几种常见方式

    public UserService(String str){
        System.out.println("有参构造实例化对象"+str);
    }

    <bean id="text" class="com.cc.service.UserService" >
        <constructor-arg name="str" value="hhhhhh"/>
    </bean>

    public UserService(String str,int string){
        System.out.println("有参构造实例化对象"+str+","+string);
    }

    <bean id="text" class="com.cc.service.UserService" >
        <constructor-arg name="str" index="0" value=""/>
        <constructor-arg name="string" index="1" value="188"/>
    </bean>

<bean id="user" class="com.cc.entity.User" factory-method="createObj"></bean>

public class User {
 
    public static Person createObj() {
        return new Person();
    }
}

public class Main {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext a = new ClassPathXmlApplicationContext("test.xml");
        Person user = (Person) a.getBean("user");
        System.out.println(user);
    }
}

    <bean id="user" class="com.cc.entity.User" ></bean>
    <bean id="person" class="com.cc.entity.Person" factory-bean="user" factory-method="createObj"></bean>

public class User {
    public User createObj() {
        return new User();
    }
}

public class Main {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext a = new ClassPathXmlApplicationContext("test.xml");
        Object bean = a.getBean("person");
        System.out.println(bean);
    }
}

public class User implements FactoryBean<Person> {
    @Override
    public Person getObject() throws Exception {
        return new Person();
    }
 
    @Override
    public Class<?> getObjectType() {
        return Person.class;
    }
}

<bean class="com.cc.entity.User" id="user"></bean>