How do we usually create objects?

Parametric and non-parametric structures

Let's see how to deal with these two situations in Spring.

Create entity classes

public class User {

    private String name;
    private String sex;
    private int age;

    public User() {
        System.out.println("User Nonparametric structure of");
    }

    public User(String name) {
        System.out.println("User Parametric structure");
        this.name = name;
    }

    public User(String name, int age) {
        System.out.println("User PARAMETRIC STRUCTURES 2");
        this.name = name;
        this.age = age;
    }

    public User(String name, String sex, int age) {
        System.out.println("User Parametric structure 3");
        this.name = name;
        this.sex = sex;
        this.age = age;
    }

    public void setName(String name) {
        System.out.println(name+":"+System.currentTimeMillis());
        this.name = name;
    }

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

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

Spring configuration file

<?xml version="1.0" encoding="UTF-8"?>
<!--suppress SpringFacetInspection -->
<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">

    <!--
    Spring Configuration file
    bean Represent an object
    alias  alias
    import  Import an additional resource
    -->

    <bean id="user" class="com.kuang.pojo.User">
        <property name="name" value="qinjiang"/>
    </bean>

    <!--Assignment using constructor parameter Subscripts-->
    <bean id="user2" class="com.kuang.pojo.User">
        <constructor-arg index="0" value="kuangshen"/>
        <constructor-arg index="1" value="18"/>
    </bean>

    <!--Assignment by name-->
    <bean id="user3" class="com.kuang.pojo.User">
        <constructor-arg name="name" value="kuangshen3"/>
        <constructor-arg name="age" value="3"/>
    </bean>

    <!--Assignment by type-->
    <bean id="user4" class="com.kuang.pojo.User">
        <constructor-arg type="java.lang.String" value="kuangshen4"/>
        <constructor-arg type="java.lang.Integer" value="18"/>
        <constructor-arg type="java.lang.String" value="male"/>
    </bean>
</beans>

Test class

public class UserTest {
    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User)context.getBean("user");
        /*
        User user = new User();
        user.setName("qinjiang");
        */
        System.out.println(user.toString());
    }

    @Test
    public void test2(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User) context.getBean("user4");
        System.out.println(user);
    }
}

Summary:

• Through parametric structure
  • Subscript subscript
  • By parameter name [recommendation]
  • By parameter type
• Through parametric structure
  • The default is constructed with no parameters

Note: There must be a parametric construction method.

For more information, check out: Create a factory model