本想每个小知识一篇随笔，但是那样，看起来有些单薄，所以，就放在一片文章里了。而且，以后还会慢慢在最后不断的追加。
目录：
FactoryBean
BeanPostProcessor
1.FactoryBean
FactoryBean接口，它在Spring框架源码内部，被大量使用，如使用AOP创建bean的代理时，使用了ProxyFactoryBean；从JNDI中查找对象时，使用了JndiObjectFactoryBean。
它在框架外，很少使用。但是为了学习，也得研究研究，您说是不？
它怎么使用？首先看看构造。
1 public interface FactoryBean<T> {
// 返回的是这个工厂管理的对象的实例
2 T getObject() throws Exception;
3 // 返回的是工厂创建的对象的类型
4 Class<?> getObjectType();
5
6 boolean isSingleton();
7
8 }
上个例子，看具体东西。
1 public class Tool {
2
3
4 private int id;
5 public Tool(int id) {
6 this.id = id;
7 }
8 public int getId() {
9 return id;
10 }
11
12 public void setId(int id) {
13 this.id = id;
14 }
15 }
1 public class ToolFactory implements FactoryBean<Tool> {
2
3 private int factoryId;
4 private int toolId;
5 // 创建的是Tool的对象
6 @Override
7 public Tool getObject() throws Exception {
8 return new Tool(toolId);
9 }
10
11 @Override
12 public Class<?> getObjectType() {
13 return Tool.class;
14 }
15
16 @Override
17 public boolean isSingleton() {
18 return false;
19 }
20
21 public int getFactoryId() {
22 return factoryId;
23 }
24
25 public int getToolId() {
26 return toolId;
27 }
28
29 public void setFactoryId(int factoryId) {
30 this.factoryId = factoryId;
31 }
32
33 public void setToolId(int toolId) {
34 this.toolId = toolId;
35 }
36
37 }
1 public class Test {
2
3 public static void main(String[] args) {
4 @SuppressWarnings("resource")
5 ApplicationContext context = new ClassPathXmlApplicationContext("beaFactoryTest.xml");
6 Tool tool = (Tool) context.getBean("tool"); // 在名字前面加 & 表示要得到工厂类的bean
7 ToolFactory tool2 = (ToolFactory) context.getBean("&tool");
8 System.out.println("Tool Id is " + tool.getId());
9 System.out.println("ToolFactory Id is " + tool2.getFactoryId());
10
11 }
12 }
1 <bean id="tool" class="com.lee.demo.beanfactory.ToolFactory"> 2 <property name="factoryId" value="9090"/> 3 <property name="toolId" value="108"/> 4 </bean>
最后执行结果：
Tool Id is 108
ToolFactory Id is 9090
2.BeanPostProcessor
它叫bean后处理器,也就是处理bean，它针对所有的bean，在初始化前后，对bean进行操作。主要内容我会在例子中描述。
例子：
1 public class HelloWorld {
2 private String message;
3
4 public void setMessage(String message) {
5 this.message = message;
6 }
7
8 public void getMessage() {
9 System.out.println("Your Message : " + message);
10 }
11
// 加上init方法和destory方法，是为了在后面验证他们和postProcessBeforeInitialization postProcessAfterInitialization 执行的先后顺序
12 public void init() {
13 System.out.println("Bean is going through init.");
14 }
15
16 public void destroy() {
17 System.out.println("Bean will destroy now.");
18 }
19 }
1 public class InitHelloWorld implements BeanPostProcessor {
2 // BeanPostProcessor 接口中主要是下面两个方法 初始化前的后处理 初始化后的后处理
3 @Override
4 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
5
6 System.out.println("BeforeInitialization : " + beanName);
7 return bean; // you can return any other object as well
8 }
9
10 @Override
11 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
12
13 System.out.println("AfterInitialization : " + beanName);
14 return bean; // you can return any other object as well
15 }
16
17 }
Test.java
1 public class Test {
2
3 public static void main(String[] args) {
4 @SuppressWarnings("resource")
5 AbstractApplicationContext context = new ClassPathXmlApplicationContext("beaFactoryTest.xml");
6 HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
7 obj.getMessage(); // 注册钩子方法
8 context.registerShutdownHook();
9 }
10 }
查看源码：
1 @Override // 在JVM运行期间，注册一个钩子关闭方法，关闭掉这个context。实际的关闭程序的操作，被代理给doClose方法。
2 public void registerShutdownHook() {
3 if (this.shutdownHook == null) {
4 // No shutdown hook registered yet.
5 this.shutdownHook = new Thread() {
6 @Override
7 public void run() {
8 doClose();
9 }
10 };
11 Runtime.getRuntime().addShutdownHook(this.shutdownHook);
12 }
13 }
xml文件
1 <bean id = "helloWorld" class = "com.lee.demo.beanfactory.HelloWorld" 2 init-method = "init" destroy-method = "destroy"> 3 <property name = "message" value = "Hello World!"/> 4 </bean> 5 6 <bean class = "com.lee.demo.beanfactory.InitHelloWorld" />
执行结果：
1 BeforeInitialization : helloWorld 2 Bean is going through init. 3 AfterInitialization : helloWorld 4 Your Message : Hello World! 5 [org.springframework.context.support.ClassPathXmlApplicationContext] - Closing org[email protected]6ae40994: startup date [Thu May 17 23:31:53 JST 2018]; root of context hierarchy 6 Bean will destroy now.
在这里大致说一下Spring的实例化过程：
实例化Bean对象→设置对象属性→检查Aware相关接口并设置相关依赖→BeanPostProcessor前置处理→检查是否是InitializingBean以决定是否调用afterPropertiesSet方法→
检查是否配置有自定义的init-method方法→BeanPostProcessor后置处理→是否实现DisposableBean接口→是否配置有自定义的destroy方法
3.Aware接口
它是干什么用的呢？作用就是通过上下文（Context)可以获得当前环境。看看它的接口：
我们拿BeanNameAware来举个例子。
1 public class User implements GetNameAware {
2
3 private String id;
4 private String name;
5 private String address;
6 @Override
7 public void setBeanName(String name) {
8 this.id = name;
9 }
10 public String getId() {
11 return id;
12 }
13 public String getName() {
14 return name;
15 }
16 public String getAddress() {
17 return address;
18 }
19 public void setId(String id) {
20 this.id = id;
21 }
22 public void setName(String name) {
23 this.name = name;
24 }
25 public void setAddress(String address) {
26 this.address = address;
27 }
28
29 }
1 public class User2 {
2
3 private String id;
4 private String name;
5 private String address;
6 public String getId() {
7 return id;
8 }
9 public String getName() {
10 return name;
11 }
12 public String getAddress() {
13 return address;
14 }
15 public void setId(String id) {
16 this.id = id;
17 }
18 public void setName(String name) {
19 this.name = name;
20 }
21 public void setAddress(String address) {
22 this.address = address;
23 }
24
25 }
1 public interface GetNameAware extends BeanNameAware {
2
3
4 }
1 public class Test {
2 public static void main(String[] args) {
3 ApplicationContext ctx = new ClassPathXmlApplicationContext("beaFactoryTest.xml");
4 User user = (User) ctx.getBean("user1");
5 User2 user2 = (User2) ctx.getBean("user2");
6 System.out.println("user id " + user.getId() + " user name " + user.getName() + " user address " + user.getAddress());
7 System.out.println("========================================");
8 System.out.println("user2 id " + user2.getId() + " user2 name " + user2.getName() + " user2 address " + user2.getAddress());
9 }
10 }
1 <bean id="user1" class="com.lee.demo.aware.User"> 2 <property name="name" value="lee"/> 3 <property name="address" value="China"/> 4 </bean> 5 6 <bean id="user2" class="com.lee.demo.aware.User2"> 7 <property name="name" value="lin"/> 8 <property name="address" value="Tokyo"/> 9 </bean>
执行结果（user id 因为继承了GetNameAware接口，对BeanName进行了设置）：
1 user id user1 user name lee user address China 2 ======================================== 3 user2 id null user2 name lin user2 address Tokyo
原文地址：https://www.cnblogs.com/lihao007/p/9053644.html
时间： 2024-11-05 21:19:01