Spring之注解注入bean
1.引入jar包。配置log4j.properties文件
2.创建Person类
package com.hy.spring.pojo;
import org.springframework.stereotype.Component;
//使用component的注解方式注入
//@Component("person"),等同于使用依赖注入方式，配置的创建Car类
package com.hy.spring.pojo;
public class Car {
private String name;
private String color;
@Override
public String toString() {
return "Car [name=" + name + ", color=" + color + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
}
3.配置applicationContext.xml
<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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="com.hy.spring.pojo">context:component-scan>
beans>
4.编写测试用例
package com.hy.spring.pojo;
import javax.annotation.Resource;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
//创建容器
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext2.xml")
public class RunWithTest {
//在bean容器中查找name为person的对象,就是我们之前在Person类中用注解component创建的bean
@Resource(name="person")
private Person p;
@Test
public void test() {
System.out.println(p);
}
}
总结
1.其他类级别的注解
@Component("person") //适用于所有层
@Service("person") //适用于Service层
@Repository("person") //适用于持久层
@Controller("person") //适用于Controller层
2.限制单例或是多例
@Component("person") //适用于所有层
@Scope(scopeName="singleton")//限制创建单例对象
//@Scope(scopeName="prototype")//限制创建多例对象
3.set方式注入value值
- 在私有的成员变量注入
@Value("BMW")
private String name;
@Value("Red")
private String color;
- 在set方法中注入
@Value("BMW")
public void setName(String name) {
this.name = name;
}
@Value("Red")
public void setColor(String color) {
this.color = color;
}
4.自动装配注解，@Autowired
注意，此处按照对象的类型进行自动装配
@Autowired
private Car mycar;
自动装配的例子
1.Person类
package com.hy.spring.pojo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("person")
public class Person {
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", mycar=" + mycar + "]";
}
private String name;
private Integer age;
@Autowired
private Car mycar;
public Person() {
super();
System.out.println("构造方法被调用");
}
public String getName() {
return name;
}
@Value("Tom")
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
@Value("18")
public void setAge(Integer age) {
this.age = age;
}
public Car getMycar() {
return mycar;
}
public void setMycar(Car mycar) {
this.mycar = mycar;
}
}
2.Car类
package com.hy.spring.pojo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("car")
public class Car {
@Value("BMW")
private String name;
@Value("Red")
private String color;
@Override
public String toString() {
return "Car [name=" + name + ", color=" + color + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
}
3.applicationContext.xml
<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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="com.hy.spring.pojo">context:component-scan>
beans>
4.测试类
package com.hy.spring.pojo;
import javax.annotation.Resource;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext2.xml")
public class RunWithTest {
@Resource(name="person")
private Person p;
@Test
public void test() {
System.out.println(p);
}
}
5.运行结果，控制台输出信息：
自动装配可能存在的问题，一个类型有多个对象，自动装配不知道装配哪个对象
如：假设applicationContext.xml配置为
<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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<bean name="car1" class="com.hy.spring.pojo.Car">
<property name="name" value="BMW1">property>
<property name="color" value="red">property>
bean>
<bean name="car2" class="com.hy.spring.pojo.Car">
<property name="name" value="BMW2">property>
<property name="color" value="blue">property>
bean>
beans>
1.可以用@Qualifier(“name”)解决，如下：
@Autowired
@Qualifier("car1")
private Car mycar;
2.可以用@Resource(name=“name”)解决，如下：
@Resource(name="car1")
private Car mycar;