Spring4自动装配(default-autowire)

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