一、Bean作用域
spring容器创建的时候,会将所有配置的bean对象创建出来,默认bean都是单例的。代码通过getBean()方法从容器获取指定的bean实例,容器首先会调用Bean类的无参构造器,创建实例对象
那么?我们如何说明出bean是单例的呢?
构建出两份学生对象,执行,发现两个对象的内存地址相同,内存中只有一份
如何使它成为多例的呢?那么则需要在配置文件中添加scope="prototype"该属性即可!
scope="prototype" 原型模式(N个对象):真正使用时才会创建,每获取一次,都会创建不同对象
scope="singleton" 单例模式:容器初始化时需要使用name建,每次获取的都是同一个对象,默认值
使用Spring通过getter访问器实现了对属性赋值,这种做法被称为设值注入。除此之外Spring还提供了通过构造方法赋值的能力,成为构造注入。
下面我们通过一个例子来深入了解一下
首先创建一个Car类
package cn.entity; public class Car {
private String color;
private String brand; public String toString() {
return "Car [color=" + color + "]";
} public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public String getBrand() {
return brand;
}
public void setBrand(String brand) {
this.brand = brand;
} }
再书写Student类
package cn.entity; public class Student {
private String name;
private String age;
private Car car; public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + ", myCar=" +car
+ "]";
}
public Car getCar() {
return car;
}
public void setCar(Car car) {
this.car = car;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
1.1设值注入(set方法注入):本质上是调用了Bean的setXXX()进行值的注入。分为普通属性和域属性
测试类:
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public class Test01 {
@Test public void addTest(){
ApplicationContext ctx= new ClassPathXmlApplicationContext( "applicationContext.xml" );
Student student=(Student) ctx.getBean( "stu" );
System.out.println(student);
} |
实现效果:
三、集合属性注入[List、Set、Map]
package cn.entity; import java.util.List;
import java.util.Map;
import java.util.Set; public class CollectionBean {
private List<String> list;
private Set<String> set;
private Map<String,String> map;
public List<String> getList() {
return list;
}
public void setList(List<String> list) {
this.list = list;
}
public Set<String> getSet() {
return set;
}
public void setSet(Set<String> set) {
this.set = set;
}
public Map<String, String> getMap() {
return map;
}
public void setMap(Map<String, String> map) {
this.map = map;
} }
applicationContext.xml配置文件书写
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:p="http://www.springframework.org/schema/p"
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="stu" class="cn.entity.Student" scope="prototype">
<property name="color" value="红色"></property>
</bean> <bean id="cars" class="cn.entity.Car" scope="prototype">
<property name="color" value="红色"></property>
</bean> <bean id="stu1" class="cn.entity.Student" scope="prototype">
<property name="name" value="章撒"></property>
<property name="age" value="12"></property>
<property name="car" value="cars"></property>
</bean> <bean id="car" class="cn.entity.Car">
<property name="color" value="红色"></property>
</bean> <bean id="stu2" class="cn.entity.Student">
<property name="name" value="张三"></property>
<property name="age" value="18"></property>
<property name="car" ref="car"></property>
</bean> <bean id="stu3" class="cn.entity.Student" p:name="李四" p:age="13" p:car-ref="car"/> <bean id="list" class="cn.entity.CollectionBean">
<property name="list">
<list>
<value>张三</value>
<value>李四</value>
</list>
</property>
</bean>
<bean id="set" class="cn.entity.CollectionBean">
<property name="set">
<set>
<value>张三1</value>
<value>李四1</value>
</set>
</property>
</bean>
<bean id="map" class="cn.entity.CollectionBean">
<property name="map">
<map>
<entry key="dq">
<value>张三2</value>
</entry>
<entry key="eq">
<value>李四2</value>
</entry>
</map>
</property>
</bean>
</beans>
测试类
package cn.test; import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; import cn.entity.CollectionBean;
import cn.entity.HappyService;
import cn.entity.Student; public class MyTest { public void listTest(){
ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
CollectionBean bean=(CollectionBean)ctx.getBean("list");
System.out.println(bean.getList()); }
@Test
public void setTest(){
ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
CollectionBean bean=(CollectionBean)ctx.getBean("set");
System.out.println(bean.getSet());
}
@Test
public void mapTest(){
ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
CollectionBean bean=(CollectionBean)ctx.getBean("map");
System.out.println(bean.getMap());
}
}
list()
set()
map()
四、基于注解的DI
注:在项目中添加Spring AOP相关的JAR文件以及xsd约束文件。
由于是基于注解的DI,所以无需再Spring配置文件中进行节点配置,只需配置包扫描器即可!
配置包扫描器用途:
该包下以及子包中的类才可以被Spring扫描,去寻找被注解的类和属性,让Spring容器管理赋值
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:p="http://www.springframework.org/schema/p"
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
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
">
指定包名
<context:component-scan base-package="cn.entitys"></context:component-scan>
</beans>
Student类:
指定@Component中的value即可在测试类中的getBean()中植入即可。
@Value为该属性赋值
等价于@Component的注解:
@Component[不分层的情况下]
@Repository() [Dao层]
@Service() [Biz层]
@Controller() [Action类]
@Component(value="stu")
public class Student {
@Value("呵呵")
private String name;
@Value("13")
private String age; /*
* JDK注解 @Resource(name="car2")
*/ /*
* Spring注解
*/
@Autowired
@Qualifier(value="car2") private Car car; @Override
public String toString() {
return "Student [name=" + name + ", age=" + age + ", car=" + car + "]";
}
Car类:
@Component(value="car2") public class Car {
@Value("黑色")
private String color;
@Value("奥迪")
private String brand; @Override
public String toString() {
return "Car [color=" + color + ", brand=" + brand + "]";
}
测试类:
public class Test01 {
@Test
public void addTest(){
ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml"); Student student=(Student) ctx.getBean("stu");
System.out.println(student);
}
}
效果展示