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