如何使用spring
1.spring容器
a.spring容器是什么?
用来管理对象的一个程序。
b.如何启动spring容器?
step1,将spring相关的jar文件拷贝到WEB-INF\lib下。
step2,在src下,添加一个配置文件applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:jee="http://www.springframework.org/schema/jee"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
</beans>
step3,启动容器。
2.容器如何管理对象?
1)如何实例化?
方式一:
容器调用不带参的构造器。
<bean id="标识符" class="Bean类"/>
方式二: (了解)
容器调用类的静态方法(静态工厂)。
使用factory-method属性指定静态方法。
<bean id="标识符" class="Bean类" factory-method="..."/>
方式三: (了解)
实例工厂。
<bean id="标识符" factory-bean="id"
factory-method="..."/>
代码示例:
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:jee="http://www.springframework.org/schema/jee"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
<!-- id要求唯一,class为完整包名.类名 -->
<bean id="eb" class="container.ExampleBean"/>
<bean id="cal" class="java.util.GregorianCalendar"/>
<bean id="student" class="container.Student"/>
<!-- 静态工厂方式 -->
<!-- factory-method必须为静态方法 -->
<bean id="cal2" class="java.util.Calendar"
factory-method="getInstance"/>
<!-- 实例化工厂方式 -->
<bean id="date1" factory-bean="cal"
factory-method="getTime"/>
</beans>
ExampleBean.java
package container;
import java.io.Serializable;
/**
* javabean
* 一个java类满足如下条件:
* a,实现序列化接口
* b,有无参构造器
* c,有属性及对应的get/set方法
*
*/
public class ExampleBean implements Serializable{
public ExampleBean(){
System.out.println("ExampleBean()构造器...");
}
}
Test.java
package container;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
public static void main(String[] args) {
String conf = "container/applicationContext.xml";
ApplicationContext ac =
new ClassPathXmlApplicationContext(conf);
Student stu = ac.getBean("student",Student.class);
System.out.println(stu);
}
}
2)作用域
容器会依据scope属性来决定创建多少个实例。默认情况下,容器对于一个bean的配置,只会创建一个实例。
scope属性值可以为以下两个
prototype:(原型),每getBean一次,就会创建一个新的实例。
singleton:(单例,缺省值),只创建一个实例。
3)生命周期相关的几个方法
类似servlet容器可以对servlet进行生命周期的管理,spring容器同样也可以对bean进行生命周期的管理。
init-method:指定初始化方法,容器在创建实例之后,会调用该实例的初始化方法。
detroy-method:指定销毁方法,容器在关闭之前,会调用该实例的销毁方法。
注意,只有当scope="singleton"时,销毁方法才起作用。
4)延迟加载(了解)
在默认情况下,容器启动之后,会将所有配置scope="singleton"的bean创建好。
如果需要延迟加载(即不事先创建好),需要将lazy-init配置为true。
在顶级的<beans/>元素中的default-lazy-init属性,可以为容器所有的<bean>指定延迟加载。
代码示例:
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:jee="http://www.springframework.org/schema/jee"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
<!--
作用域:scope
prototype:(原型),每getBean都创建一个新的实例。
singleton:(单例,缺省值),只创建一个实例。
-->
<!--
<bean id="mb" class="container.other.MessageBean"
scope="prototype"/>
-->
<!--
生命周期相关的方法
init-method:指定初始化方法,容器在创建实例之后,会调用该实例的初始化方法
destroy-method:指定销毁方法,容器在关闭之前,会调用该实例的销毁方法。
注:销毁方法只有scope="singleton"时,销毁方法才会被调用。
-->
<!--
<bean id="mb" class="container.other.MessageBean"
init-method="init" destroy-method="destroy"/>
-->
<!--
延迟加载
lazy-init="true"表示延迟加载,在getBean时才创建实例。
默认情况容器会将所有scope属性
为singleton的bean创建好。
-->
<bean id="mb" class="container.other.MessageBean"
lazy-init="true"/>
</beans>
MessageBean.java
package container.other;
import java.io.Serializable;
public class MessageBean implements Serializable{
public MessageBean(){
System.out.println("MessageBean构造器...");
}
public void init(){
System.out.println("MessageBean的init方法被调用...");
}
public void sendMessage(){
System.out.println("MessageBean的sendMessage方法被调用..");
}
public void destroy(){
System.out.println("MessageBean的destroy方法被调用..");
}
}
TestCase.java
package container.other;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class TestCase {
//@Test
//演示作用域
public void test1(){
//启动spring容器
ApplicationContext ac =
new ClassPathXmlApplicationContext(
"container/other/applicationContext.xml");
//获得bean实例
MessageBean mb = ac.getBean("mb",MessageBean.class);
MessageBean mb2 = ac.getBean("mb",MessageBean.class);
System.out.println(mb==mb2);
}
//演示生命周期相关的几个方法
//@Test
public void test2(){
//启动spring容器
//ApplicationContext接口中没有定义close方法,需要
//使用其子类型
AbstractApplicationContext ac =
new ClassPathXmlApplicationContext(
"container/other/applicationContext.xml");
//获得bean实例
MessageBean mb = ac.getBean("mb",MessageBean.class);
mb.sendMessage();
//关闭容器
ac.close();
}
//演示延迟加载
@Test
public void test3(){
ApplicationContext ac =
new ClassPathXmlApplicationContext(
"container/other/applicationContext.xml");
MessageBean mb = ac.getBean("mb",MessageBean.class);
}
}