spring5教程（二）——core
ioc容器和beans
IOC也叫DI，org.springframework.beans and org.springframework.context 是ioc容器的基础包。BeanFactory接口提供基础功能，ApplicationContext 是BeanFactory的扩展。
代码
services.xml
<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="petStore" class="org.springframework.samples.jpetstore.services.PetStoreServiceImpl">
<property name="accountDao" ref="accountDao"/>
<property name="itemDao" ref="itemDao"/>
bean>
beans>daos.xml
<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="accountDao"
class="org.springframework.samples.jpetstore.dao.jpa.JpaAccountDao">
bean>
<bean id="itemDao" class="org.springframework.samples.jpetstore.dao.jpa.JpaItemDao">
bean>
beans><beans>
<import resource="services.xml"/>
<import resource="resources/messageSource.xml"/>
<import resource="/resources/themeSource.xml"/>
<bean id="bean1" class="..."/>
<bean id="bean2" class="..."/>
beans>// create and configure beans
ApplicationContext context = new ClassPathXmlApplicationContext("services.xml", "daos.xml");
// retrieve configured instance
PetStoreService service = context.getBean("petStore", PetStoreService.class);
// use configured instance
List<String> userList = service.getUsernameList();bean配置属性
静态方法注入
"clientService"
class="examples.ClientService"
factory-method="createInstance"/> public class ClientService {
private static ClientService clientService = new ClientService();
private ClientService() {}
public static ClientService createInstance() {
return clientService;
}
}非静态方法注入
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
bean>
<bean id="clientService"
factory-bean="serviceLocator"
factory-method="createClientServiceInstance"/>public class DefaultServiceLocator {
private static ClientService clientService = new ClientServiceImpl();
public ClientService createClientServiceInstance() {
return clientService;
}
}一个工厂多个方法
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
bean>
<bean id="clientService"
factory-bean="serviceLocator"
factory-method="createClientServiceInstance"/>
<bean id="accountService"
factory-bean="serviceLocator"
factory-method="createAccountServiceInstance"/>public class DefaultServiceLocator {
private static ClientService clientService = new ClientServiceImpl();
private static AccountService accountService = new AccountServiceImpl();
public ClientService createClientServiceInstance() {
return clientService;
}
public AccountService createAccountServiceInstance() {
return accountService;
}
}构造器注入
package x.y;
public class Foo {
public Foo(Bar bar, Baz baz) {
// ...
}
}<beans>
<bean id="foo" class="x.y.Foo">
<constructor-arg ref="bar"/>
<constructor-arg ref="baz"/>
bean>
<bean id="bar" class="x.y.Bar"/>
<bean id="baz" class="x.y.Baz"/>
beans>构造器注入参数问题
package examples;
public class ExampleBean {
// Number of years to calculate the Ultimate Answer
private int years;
// The Answer to Life, the Universe, and Everything
private String ultimateAnswer;
public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}
}"exampleBean" class="examples.ExampleBean">
type="int" value="7500000"/>
type="java.lang.String" value="42"/>
<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg index="0" value="7500000"/>
<constructor-arg index="1" value="42"/>
bean><bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg name="years" value="7500000"/>
<constructor-arg name="ultimateAnswer" value="42"/>
bean>
构造函数别名
package examples;
public class ExampleBean {
// Fields omitted
@ConstructorProperties({"years", "ultimateAnswer"})
public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}
}Collections
<bean id="moreComplexObject" class="example.ComplexObject">
<property name="adminEmails">
<props>
<prop key="administrator">[email protected]prop>
<prop key="support">[email protected]prop>
<prop key="development">[email protected]prop>
props>
property>
<property name="someList">
<list>
<value>a list element followed by a referencevalue>
<ref bean="myDataSource" />
list>
property>
<property name="someMap">
<map>
<entry key="an entry" value="just some string"/>
<entry key ="a ref" value-ref="myDataSource"/>
map>
property>
<property name="someSet">
<set>
<value>just some stringvalue>
<ref bean="myDataSource" />
set>
property>
bean>p标签简化配置
"http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
name="john-classic" class="com.example.Person">
<property name="name" value="John Doe"/>
<property name="spouse" ref="jane"/>
name="john-modern"
class="com.example.Person"
p:name="John Doe"
p:spouse-ref="jane"/>
name="jane" class="com.example.Person">
<property name="name" value="Jane Doe"/>
c标签简化配置
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:c="http://www.springframework.org/schema/c"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="bar" class="x.y.Bar"/>
<bean id="baz" class="x.y.Baz"/>
<bean id="foo" class="x.y.Foo">
<constructor-arg ref="bar"/>
<constructor-arg ref="baz"/>
<constructor-arg value="[email protected]"/>
bean>
<bean id="foo" class="x.y.Foo" c:bar-ref="bar" c:baz-ref="baz" c:email="[email protected]"/>
beans>
<bean id="foo" class="x.y.Foo" c:_0-ref="bar" c:_1-ref="baz"/>depends-on
id="beanOne" class="ExampleBean" depends-on="manager,accountDao">
<property name="manager" ref="manager" />
id="manager" class="ManagerBean" />
id="accountDao" class="x.y.jdbc.JdbcAccountDao" /> Lazy-initialized
id="lazy" class="com.foo.ExpensiveToCreateBean" lazy-init="true"/>
name="not.lazy" class="com.foo.AnotherBean"/> <beans default-lazy-init="true">
beans>init-method
"exampleInitBean" class="examples.ExampleBean" init-method="init"/>
public class ExampleBean {
public void init() {
// do some initialization work
}
} 类似于
"exampleInitBean" class="examples.AnotherExampleBean"/>
public class AnotherExampleBean implements InitializingBean {
public void afterPropertiesSet() {
// do some initialization work
}
} destroy-method
"exampleInitBean" class="examples.ExampleBean" destroy-method="cleanup"/>
public class ExampleBean {
public void cleanup() {
// do some destruction work (like releasing pooled connections)
}
} 类似于
"exampleInitBean" class="examples.AnotherExampleBean"/>
public class AnotherExampleBean implements DisposableBean {
public void destroy() {
// do some destruction work (like releasing pooled connections)
}
} 注解方式 init-method destroy-method
public class CachingMovieLister {
@PostConstruct
public void populateMovieCache() {
// populates the movie cache upon initialization...
}
@PreDestroy
public void clearMovieCache() {
// clears the movie cache upon destruction...
}
}
读取配置文件
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations" value="classpath:com/foo/jdbc.properties"/>
id="dataSource" destroy-method="close"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
Spring Bean 作用域
singleton 该作用域将 bean 的定义的限制在每一个 Spring IoC 容器中的一个单一实例(默认)。
prototype 该作用域将单一 bean 的定义限制在任意数量的对象实例。
request 该作用域将 bean 的定义限制为 HTTP 请求。只在 web-aware Spring ApplicationContext 的上下文中有效。
session 该作用域将 bean 的定义限制为 HTTP 会话。 只在web-aware Spring ApplicationContext的上下文中有效。
global-session 该作用域将 bean 的定义限制为全局 HTTP 会话。只在 web-aware Spring ApplicationContext 的上下文中有效。