xml方式注入空值

可以通过 xml 配置的方式， 让 Spring 帮我们创建对象的时候注入一个 null 值

Student.java

package com.ctguyxr.spring5.entity;
/**
* Created by Intellij IDEA 2021.3
* @author: Xinrui Yu
* @date: 2021/12/9 10:25
*/
public class Student {
    private Integer id;
    private String name;
    private String gender;
    public Student() {
    }
    public Student(Integer id, String name, String gender) {
        this.id = id;
        this.name = name;
        this.gender = gender;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                '}';
    }
}

xml配置

<?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="student" class="com.ctguyxr.spring5.entity.Student">
        <property name="id" value="1" />
        <property name="name" value="yxr" />
        <property name="gender">
            <!--null标签用来配置属性的null值-->
            <null/>
        </property>
    </bean>
</beans>

测试

@Test
public void test2(){
    ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");
    Student student = context.getBean("student", Student.class);
    System.out.println(student);
}