Spring探究-----自动装配Bean详解

1.xml配置文件（了解）

1.1 byName 按名称自动装配（推荐，需要get和set方法）

根据类型进行自动装配. 但要求 IOC 容器中只有一个类型对应的 bean, 若有多个则无法完成自动装配

    <bean id="student" class="com.spring.autowire.Student" autowire="byName">
        <property name="stuName" value="小魔仙"></property>
    </bean>

    <bean id="address" class="com.spring.autowire.Address">
        <property name="addressInfo" value="一中"></property>
    </bean>

1.2 btType 按类型自动装配

若属性名和某一个 bean 的 id 名一致, 即可完成自动装配. 若没有 id 一致的, 则无法完成自动装配

<bean id="student" class="com.spring.autowire.Student" autowire="byType">
        <property name="stuName" value="小魔仙"></property>
    </bean>

    <bean id="address" class="com.spring.autowire.Address">
        <property name="addressInfo" value="一中"></property>
    </bean>

1.3 全局autowire

<?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" default-autowire="byName">

</beans>

   2.注解装配（熟悉）

2.1 @Autowired

@Autowired是按类型自动转配的

@Autowired
private School school;

<bean id="school" class="com.spring.autowire.School">
       <property name="schoolName" value="一中"></property>
</bean>

2.2 @Qualifier

@Autowired是根据类型自动装配的，加上@Qualifier则可以根据byName的方式自动装配，其中@Qualifier不能单独使用

@Autowired
@Qualifier("schoolName")
private School school;

<bean id="schoolName" class="com.spring.autowire.School">
     <property name="schoolName" value="一中"></property>
</bean>

2.3 @Resource

@Resource如有指定的name属性，先按该属性进行byName方式查找装配；其次再进行默认的byName方式进行装配；如果以上都不成功，则按byType的方式自动装配。都不成功，则报异常

@Resource
private School school;

<bean id="school" class="com.spring.autowire.School">
     <property name="schoolName" value="一中"></property>
</bean>

或者

@Resource(name="schoolName")
private School school;

<bean id="schoolName" class="com.spring.autowire.School">
    <property name="schoolName" value="一中"></property>
</bean>

完整Demo

package com.spring.autowire;

import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

/**
 * 学生类
 *
 * @author yyx 2019年6月9日
 */
public class Student {
    /**
     * 学生姓名
     */
    private String stuName;
    /**
     * 学校信息
     */
    @Autowired
    private School school;
    /**
     * 地址信息
     */
    private Address address;

    public String getStuName() {
        return stuName;
    }

    public void setStuName(String stuName) {
        this.stuName = stuName;
    }    

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Student [stuName=" + stuName + ", school=" + school + ", address=" + address + "]";
    }
}

package com.spring.autowire;

/**
 * 地址类
 *
 * @author yyx 2019年6月9日
 */
public class Address {
    /**
     * 地址信息
     */
    private String addressInfo;

    public String getAddressInfo() {
        return addressInfo;
    }

    public void setAddressInfo(String addressInfo) {
        this.addressInfo = addressInfo;
    }

    @Override
    public String toString() {
        return "Address [addressInfo=" + addressInfo + "]";
    }
}

package com.spring.autowire;

/**
 * 学校类
 *
 * @author yyx 2019年6月9日
 */
public class School {
    /**
     * 学校名称
     */
    private String schoolName;

    public String getSchoolName() {
        return schoolName;
    }

    public void setSchoolName(String schoolName) {
        this.schoolName = schoolName;
    }

    @Override
    public String toString() {
        return "School [schoolName=" + schoolName + "]";
    }
}

package com.spring.autowire;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * 测试自动装配
 *
 * @author yyx 2019年6月9日
 */
public class AutowireMain {
    public static void main(String[] args) {
        ApplicationContext aContext = null;
        try {
            aContext = new ClassPathXmlApplicationContext("applicationContext.xml");
            Student student = (Student) aContext.getBean("student");
            System.out.println(student);
        } catch (Exception e) {

        }
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    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
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd
    ">

    <context:component-scan base-package="com.spring.autowire" resource-pattern="com.spring.autowire.Student"></context:component-scan>

    <!-- byType: 根据类型进行自动装配. 但要求 IOC 容器中只有一个类型对应的 bean, 若有多个则无法完成自动装配. byName:
        若属性名和某一个 bean 的 id 名一致, 即可完成自动装配. 若没有 id 一致的, 则无法完成自动装配 -->
    <bean id="student" class="com.spring.autowire.Student" autowire="byName">
        <property name="stuName" value="小魔仙"></property>
    </bean>

    <bean id="address" class="com.spring.autowire.Address">
        <property name="addressInfo" value="湖口"></property>
    </bean>

    <bean id="school" class="com.spring.autowire.School">
       <property name="schoolName" value="一中"></property>
    </bean>
</beans>

原文地址：https://www.cnblogs.com/fengfuwanliu/p/10992645.html