自动装配与兼容性

自动装配的概念

1)手动装配：以value或ref的方式明确指定属性值都是手动装配。2)自动装配：根据指定的装配规则，不需要明确指定，Spring自动将匹配的属性值注入bean中。

写几个类方便后续的测试：

public class Emp { private Integer eid; private String ename; private Car car; private Dept dept; public Integer getEid() { return eid; } public void setEid(Integer eid) { this.eid = eid; } public String getEname() { return ename; } public void setEname(String ename) { this.ename = ename; } public Car getCar() { return car; } public void setCar(Car car) { this.car = car; } public Dept getDept() { return dept; } public void setDept(Dept dept) { this.dept = dept; } @Override public String toString() { return "Emp{" + "eid=" + eid + ", ename='" + ename + '\'' + ", car=" + car + ", dept=" + dept + '}'; } } public class Dept { private Integer did; private String dname; public Integer getDid() { return did; } public void setDid(Integer did) { this.did = did; } public String getDname() { return dname; } public void setDname(String dname) { this.dname = dname; } @Override public String toString() { return "Dept{" + "did=" + did + ", dname='" + dname + '\'' + '}'; } } public class Car { private Integer cid; private String cname; @Override public String toString() { return "Car{" + "cid=" + cid + ", cname='" + cname + '\'' + '}'; } public Integer getCid() { return cid; } public void setCid(Integer cid) { this.cid = cid; } public String getCname() { return cname; } public void setCname(String cname) { this.cname = cname; } }

这里我们写一个配置文件并测试手动装配：

<?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="emp" class="com.atguigu.spring.day02_Spring.Auto.Emp" > <property name="eid" value="1001"/> <property name="ename" value="亚索"/> <property name="car" ref="car"/> <property name="dept" ref="dept"/> </bean> <bean id="car" class="com.atguigu.spring.day02_Spring.Auto.Car"> <property name="cid" value="10010"/> <property name="cname" value="兰博基尼"/> </bean> <bean id="dept" class="com.atguigu.spring.day02_Spring.Auto.Dept"> <property name="did" value="10086"/> <property name="dname" value="管理组"/> </bean> </beans>

测试：

public class Test { public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("auto.xml"); Emp emp = ac.getBean("emp", Emp.class); System.out.println(emp); } }

输出结果： 装配模式

1)根据类型自动装配：将类型匹配的bean作为属性注入到另一个bean中。若IOC容器中有多个与目标bean类型一致的bean，Spring将无法判定哪个bean最合适该属性，所以不能执行自动装配。向上兼容，可以赋值给其父类或者接口。 <?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="emp" class="com.atguigu.spring.day02_Spring.Auto.Emp" autowire="byType"> <property name="eid" value="1001"/> <property name="ename" value="亚索"/> </bean> <bean id="car1" class="com.atguigu.spring.day02_Spring.Auto.Car"> <property name="cid" value="10010"/> <property name="cname" value="兰博基尼"/> </bean> <bean id="dept1" class="com.atguigu.spring.day02_Spring.Auto.Dept"> <property name="did" value="10086"/> <property name="dname" value="管理组"/> </bean> </beans>

这里是byType，目标的bean的id名称可不与属性名一致

2)根据名称自动装配：必须将目标bean的名称和属性名设置的完全相同 <?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="emp" class="com.atguigu.spring.day02_Spring.Auto.Emp" autowire="byName"> <property name="eid" value="1001"/> <property name="ename" value="亚索"/> </bean> <bean id="car" class="com.atguigu.spring.day02_Spring.Auto.Car"> <property name="cid" value="10010"/> <property name="cname" value="兰博基尼"/> </bean> <bean id="dept" class="com.atguigu.spring.day02_Spring.Auto.Dept"> <property name="did" value="10086"/> <property name="dname" value="管理组"/> </bean> </beans>

测试：

3)通过构造器自动装配：当bean中存在多个构造器时，此种自动装配方式将会很复杂。不推荐使用。

相对于使用注解的方式实现的自动装配，在XML文档中进行的自动装配略显笨拙，在项目中更多的使用注解的方式实现。