Spring bean 四种注入方式详解

2024-04-02 19:04:59 856人浏览独家记忆

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摘要

目录一、Set方式注入pojo层：1.xml 文件test测试二、构造函数方式注入pojo层2.xml文件test测试三、注解注入pojo层3.xml文件test测试四、JavaCo

一、Set方式注入

pojo层：



public class Student1 {
    public String name;
    public String school;
    public void setName(String name) {
        this.name = name;
    }
    public void setSchool(String school) {
        this.school = school;
    }
    @Override
    public String toString() {
        return "Student1{" +
                "name='" + name + '\'' +
                ", school='" + school + '\'' +
                '}';
    }
}

1.xml 文件


<?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">
    <!--set方式注入
        id是注入bean中的名字
        class 是全限定类名
        property 是按照set方式注入
    -->
    <bean id="student1" class="com.crush.pojo.Student1">
        <property name="name" value="wyh1"/>
        <property name="school" value="hngy1"/>
    </bean>
</beans>

test测试


 @Test
    public void student1(){
        ApplicationContext context = new ClassPathXmlApplicationContext("student1.xml");
        Student1 student1 = context.getBean("student1", Student1.class);
        System.out.println(student1);
    }

二、构造函数方式注入

pojo层



public class Student2 {
    private String name;
    private String school;
    public Student2(String name, String school) {
        this.name = name;
        this.school = school;
    }
    @Override
    public String toString() {
        return "Student2{" +
                "name='" + name + '\'' +
                ", school='" + school + '\'' +
                '}';
    }
}

2.xml文件


<?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">
    <!--set方式注入
        id是注入bean中的名字
        class 是全限定类名
        constructor 是按照构造方式注入
        index 是按照成员变量在构造函数中的参数的第几个
        name 表示成员变量名
        type 表示类型
        value 表示值
        ref 表示引用 可引用另外一个注入到Spring的中的值
    -->
    <bean id="student2" class="com.crush.pojo.Student2">
        <constructor-arg index="0"  name="name" type="java.lang.String" value="wyh2"/>
        <constructor-arg name="school" value="hngy2"/>
    </bean>
</beans>

test测试


   @Test
    public void student2(){
        ApplicationContext context = new ClassPathXmlApplicationContext("student2.xml");
        Student2 student2 = context.getBean("student2", Student2.class);
        System.out.println(student2);
    }

三、注解注入

pojo层



@Component
public class Student3 {
    @Value("wyh3")
    private String name;
    @Value("hngy3")
    private String school;
    @Override
    public String toString() {
        return "Student3{" +
                "name='" + name + '\'' +
                ", school='" + school + '\'' +
                '}';
    }
}

3.xml文件


<?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:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--注解方式注入
        需要扫描注解在的包 注解才会生效
    -->
    <context:component-scan base-package="com.crush.pojo"/>
</beans>

test测试


   @Test
    public void student3(){
        ApplicationContext context = new ClassPathXmlApplicationContext("student3.xml");
        Student3 student3 = context.getBean("student3", Student3.class);
        System.out.println(student3);
    }

四、JavaConfig 方式注入

pojo层



public class Student4 {
    @Value("wyh4")
    private String name;
    @Value("hngy4")
    private String school;
    @Override
    public String toString() {
        return "Student4{" +
                "name='" + name + '\'' +
                ", school='" + school + '\'' +
                '}';
    }
}

JavaConfig 类


@Configuration
public class Student4Config {
    @Bean
    public Student4 student4(){
        return new Student4();
    }
}

xml文件扫描包


<?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:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="com.crush.config"/>
</beans>

测试：


    @Test
    public void student4(){
        ApplicationContext context = new ClassPathXmlApplicationContext("student4.xml");
        Student4 student4 = context.getBean("student4", Student4.class);
        System.out.println(student4);
    }

五、Service层注入详解

service



public interface StudentService1 {
    void test();
}

serviceImpl



public class StudentService1Impl implements StudentService1{
    @Override
    public void test() {
        System.out.println("===StudentDao1Impl===");
    }
}

xml配置文件


<?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="studentService1" class="com.crush.dao.StudentService1" />
</beans>