Spring4自动装配(default-autowire) (转)

原文地址：http://blog.csdn.net/conglinyu/article/details/63684957

Spring 自动装配



通过配置default-autowire 属性，Spring IOC 容器可以自动为程序注入bean；默认是no，不启用自动装配；
default-autowire 的类型有byName,byType,constructor；
byName：通过名称进行自动匹配；
byType：根据类型进行自动匹配；
constructor：和byType 类似，只不过它是根据构造方法注入而言的，根据类型，自动注入；


建议：自动装配机制慎用，它屏蔽了装配细节，容易产生潜在的错误；




【byName】

<?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"
        default-autowire="byName">


    <bean id="car2" class="com.zhiqi.model.Car">
        <property name="id" value="2007"></property>
        <property name="carName" value="奥迪"></property>
    </bean>
    <!-- 自动装配 byName 来找car -->
    <bean id="car" class="com.zhiqi.model.Car">
        <property name="id" value="2009"></property>
        <property name="carName" value="奥拓"></property>
    </bean>


    <bean id="employee" class="com.zhiqi.model.Employee">
        <property name="id" value="10080"></property>
        <property name="name" value="贾经理"></property>
        <property name="sex" value="男"></property>


    </bean>

</beans>

实体类

public class Car {


    private int id;
    private String carName;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getCarName() {
        return carName;
    }
    public void setCarName(String carName) {
        this.carName = carName;
    }
}

public class Employee {


    private int id;
    private String name;
    private String sex;
    private Car car;


    public Employee() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Employee(int id, String name, String sex) {
        super();
        this.id = id;
        this.name = name;
        this.sex = sex;
    }


    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Car getCar() {
        return car;
    }
    public void setCar(Car car) {
        this.car = car;
    }
}

测试：

public class MyTest {

    public static void main(String[] args) {
        ApplicationContext ac=new ClassPathXmlApplicationContext("beans.xml");
        Employee employee=(Employee)ac.getBean("employee");
        //employee.setName("李经理");//在xml中属性注入
        System.out.println(employee.getCar().getCarName());


    }
}

【byType】

<?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"
        default-autowire="byType">

    <!-- 自动装配 byType 有两个相同类型会报错 -->
    <bean id="car2" class="com.zhiqi.model.Car">
        <property name="id" value="2007"></property>
        <property name="carName" value="奥迪"></property>
    </bean>
    <!-- 自动装配 byType 来找car -->
    <bean id="car" class="com.zhiqi.model.Car">
        <property name="id" value="2009"></property>
        <property name="carName" value="奥拓"></property>
    </bean>

    <bean id="employee" class="com.zhiqi.model.Employee">
        <property name="id" value="10080"></property>
        <property name="name" value="贾经理"></property>
        <property name="sex" value="男"></property>

    </bean>

</beans>

测试：

public class MyTest {

    public static void main(String[] args) {
        ApplicationContext ac=new ClassPathXmlApplicationContext("beans.xml");
        Employee employee=(Employee)ac.getBean("employee");
        //employee.setName("李经理");//在xml中属性注入
        System.out.println(employee.getCar().getCarName());

    }
}

运行：

【default-autowire="constructor"】

<?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"
        default-autowire="constructor">

    <!-- 自动装配 constructor 需要写单参构造方法 -->
    <bean id="car3" class="com.zhiqi.model.Car">
        <property name="id" value="2007"></property>
        <property name="carName" value="奥迪"></property>
    </bean>


    <bean id="employee" class="com.zhiqi.model.Employee">
        <property name="id" value="10080"></property>
        <property name="name" value="贾经理"></property>
        <property name="sex" value="男"></property>

    </bean>

</beans>

自动装配 constructor 需要写单参构造方法

不写的话会报告错误