案例二：注入其他型別屬性（空值）

（1）建立類，定義屬性和對應的set方法

package com.orz.spring.test2;

/**
 * @author orz
 * @create 2020-08-14 15:57
 */
//1.建立類

public class Book2 {

    //2.定義屬性

    private String bname;
    private String bauthor;

    //3.提供屬性的set方法

    public void setBname(String bname) {
        this.bname = bname;
    }

    public void setBauthor(String bauthor) {
 
        this.bauthor = bauthor;
    }

    @Override
    public String toString() {
        return "Book{" +
                "bname='" + bname + '\'' +
                ", bauthor='" + bauthor + '\'' +
                '}';
    }
}

（2）在spring配置檔案中先配置物件建立，再配置屬性注入

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!-- 1.配置物件建立   -->
    <bean id="book2" class="com.orz.spring.test2.Book2">
 
        <!--  2.屬性注入      -->
        <!--     使用property完成屬性注入
         name：類裡面的屬性名稱
         value：向屬性注入的值
        -->
        <property name="bname" value="降龍十八掌"></property>
        <!--  3.使用property   null 注入空值      -->
        <property name="bauthor">
           <null></null>
        </property>
    </bean>
</beans>

（3）測試

package com.orz.spring.test2;

import com.orz.spring.test2.Book2;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author orz
 * @create 2020-08-14 16:01
 */
public class Test1 {
    @Test
    public void test1()
    {
        //1.載入spring配置檔案
        ApplicationContext context=new ClassPathXmlApplicationContext("bean2.xml");
        //2.獲取配置檔案的建立物件
        Book2 book = context.getBean("book2", Book2.class);
        //3
        System.out.println(book);
    }
}

（4）結果

Book{bname='降龍十八掌', bauthor='null'}