Spring基于XML的DI之设值注入

落日映苍穹つ 2023-10-17 12:04 56阅读 0赞

## Spring基于XML的DI之设值注入 ##

### 什么是注入 ###

##### Bean实例在调用无参构造器创建了空值对象后，就要对Bean对象的属性进行初始化。初始化是由容器自动完成的，称为注入       #####

### 注入分类 ###

##### 根据注入方式的不同，常用的有两类：设置注入、构造注入；还有一种是实现特定接口注入，由于这种注入方式采用了入侵编程，污染了代码，所以几乎不用。       #####

#### 设值注入       ####

##### 设值注入是指，通过setter方法传入被调用者的实例。这种注入方法简单、直观，因而在Spring的依赖注入中大量使用。       #####

#### 栗子       ####

##### Student.java #####

package com.hk.spring.di01;
    
    public class Student {
        
    
        private String name;
        private int age;
        private School school;//域属性
        public void setName(String name) {
            this.name = name;
        }
        public void setAge(int age) {
            this.age = age;
        }
    
        public void setSchool(School school) {
            this.school = school;
        }
        @Override
        public String toString() {
            return "Student [name=" + name + ", age=" + age + ", school=" + school
                    + "]";
        }
    
    
    }

##### School.java #####

package com.hk.spring.di01;
    
    public class School {
        
    
        private String schloolName;
    
        public void setSchloolName(String schloolName) {
            this.schloolName = schloolName;
        }
    
        @Override
        public String toString() {
            return "School [schloolName=" + schloolName + "]";
        }
    
    }

##### applicationContext.xml #####

<?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="mySchool" class="com.hk.spring.di01.School">
            <property name="schloolName" value="红林小学"/>
        </bean>
        <bean id="myStudent" class="com.hk.spring.di01.Student">
            
            <property name="name" value="张三"/>
            <property name="age" value="9"/>
            
            <property name="school" ref="mySchool"/>
        </bean>
    </beans>

##### 测试类 #####

package com.hk.spring.di01;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class Mytest {
        @Test
        public void test1(){
            String resource = "com/hk/spring/di01/applicationContext.xml";
            ApplicationContext ac = new ClassPathXmlApplicationContext(resource);
            Student stu = (Student) ac.getBean("myStudent");
            System.out.println(stu);
    
        }
    }

##### 结果 #####

Student [name=张三, age=9, school=School [schloolName=红林小学]]