Spring 基礎學習筆記 下
Aware
Spring中定義了一系列Aware接口,可用於感知spring container,獲取container中的信息,bean的信息。
例如 ApplicationContextAware可以獲取object所在的ApplicationContext,BeanNameAware可用於獲取object所在bean的名稱。
public class Cat implements ApplicationContextAware,BeanNameAware{
private Card card;
private ApplicationContext context;
// other methods ...
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.context = applicationContext;
}
@Override
public void setBeanName(String name) {
System.out.println("Bean name is " + name);
}
}
LifeCycle Callbacks
- 使用 AbstractApplicationContext 註冊hook
(1) Sound.java 中 添加
AbstractApplicationContext context = new ClassPathXmlApplicationContext("SpringConfig.xml");
context.registerShutdownHook();
(2)Cat 實現 InitializingBean,DisposableBean
public class Cat implements InitializingBean{...}
或者 自定義函數 並在xml中添加 init-method/destroy-method 指向自定義的函數名。
// Cat.java 添加方法
public void myInit() {
System.out.println("This is my init method");
}
// xml
<bean id="cat" class="hello.Cat" autowire="byName" init-method="myInit"></bean>
BeanPostProcessor & BeanFactoryPostProcessor
Bean實例化前後,添加自定義操作
新建Display.java
// Display.java
public class Display implements BeanPostProcessor{
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("Before Bean "+beanName+" init...");
return null;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("Bean "+beanName+" finished...");
return null;
}
<bean class="hello.Display"></bean>
}
// xml 添加
<bean class="hello.Display"></bean>
如果需要在BeanFactory 初始化前操作,使用BeanFactorPostProcessory用法與上面的類似。
Annotation 注入
@AutoWired: 按名字注入
@Qulifier(“relatedCard”) xml中找尋qulifier標籤中value是relatedCard的
@Resource(name=“card”) xml找bean id=card的注入
public class Cat{
private Card card;
public void sound() {
System.out.println(this.card.toString()+" sound: Meow Meow Meow");
}
// setters and getters
public Card getCard() {
return card;
}
@Autowired
public void setCard(Card card) {
this.card = card;
}
public void myInit() {
System.out.println("This is my init method");
}
}
// xml
<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"></bean>
超好用的 @Component
之前的xml中每個bean都有對應的標籤,這個實在很麻煩,spring提供了Component annotation可以標誌一個類屬於Spring Container
// Cat.java
@Component
public class Cat{
private Card card;
public void sound() {
System.out.println(this.card.toString()+" sound: Meow Meow Meow");
}
// setters and getters
public Card getCard() {
return card;
}
@Autowired
public void setCard(Card card) {
this.card = card;
}
@PostConstruct
public void myInit() {
System.out.println("This is my init method");
}
@PreDestroy
public void myDestory() {
System.out.println("This is my destory");
}
}
// xml
<bean id="card" class="hello.Card">
<property name="name" value="Jack"></property>
<property name="type" value="SmallCat"></property>
</bean>
<context:annotation-config></context:annotation-config>
<context:component-scan base-package="hello"></context:component-scan>
除了@Component 之外 @Repository、@Service、@Controller 都可起到同樣的效果。由於Spring會把@Repository標誌的類封裝成Spring 數據訪問異常類型,因此只能用於Dao層。其他幾個與Component意義不同,但作用一致。
@Component 泛化,都可用
@Repository 只可Dao層
@Service 業務層,但是目前該功能與 @Component 相同
@Controller 控制層,但是目前該功能與 @Component 相同
從 properties 文件獲取信息
// mymessage.properties
greeting=Hello
//sound.java
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("SpringConfig.xml");
String text = context.getMessage("greeting", null,"Defaule Message", null);
System.out.println(text);
}
// xml
<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
<property name="basenames">
<list>
<value>mymessages</value>
</list>
</property>
</bean>