监听者模式示例

public class SwitchMain { public static void main(String[] args) { Switch switchTest = new Switch(); switchTest.addListener(new SwitchListener() { public void handle(SwitchEvent switchEvent) { //Do what ever you want ! System.out.println("可对该事件进行二次处理: "+switchEvent.getSwitchState()); } public void handle() { //SwitchListener=callBack System.out.println("回调执行复杂操作"); } }); //触发 switchTest.call(); switchTest.close(); } } /* * 类似于Swing中的button * 1.添加监听者 * 2.定义事件同时通知监听者 */ class Switch { private SwitchListener callBack; public void addListener(SwitchListener callBack){ this.callBack = callBack; } //此时为回调方法 没有监听者概念 public void call(){ callBack.handle(); //SwitchEvent switchEvent = new SwitchEvent( this, "关"); //callBack.handle(switchEvent); } public void close(){ SwitchEvent switchEvent = new SwitchEvent( this, "关"); notifyListeners(switchEvent); } private void notifyListeners (SwitchEvent switchEvent) { callBack.handle(switchEvent); } } class SwitchEvent { private String switchState; //表示开关的状态 public SwitchEvent(Switch source, String switchState) { this.switchState = switchState; } public void setSwitchState(String switchState) { this.switchState = switchState; } public String getSwitchState() { return switchState; } } interface SwitchListener { //SwitchListener=callBack() void handle();//基于回调的观察者模式 void handle(SwitchEvent event);//支持指定处理事件 }

示例2:监听文件的变化

import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; public class App{ public static void main( String[] args ) { List<ModulesListener> modules = new ArrayList<ModulesListener>(); ModulesListener listener = new ModulesListener("custom.properties"); listener.addConfigurationListener(new ConfigurationListener() { public void configurationChanged(ConfigurationEvent event) { System.out.println("ConfigurationListener, " + event.getType() + ", " + event.getModules()); } }); listener.addKeyListener("name", new PropertiesKeyListener() { public void configurationChanged(ConfigurationEvent event, String key, String value) { System.out.println("PropertiesKeyListener, " + key + " = " + value); } }); ModulesListener listener2 = new ModulesListener("system.properties"); listener2.addConfigurationListener(new ConfigurationListener() { public void configurationChanged(ConfigurationEvent event) { System.out.println("ConfigurationListener2, " + event.getType() + ", " + event.getModules()); } }); listener2.addKeyListener("name", new PropertiesKeyListener() { public void configurationChanged(ConfigurationEvent event, String key, String value) { System.out.println("PropertiesKeyListener2, " + key + " = " + value); } }); modules.add(listener); modules.add(listener2); SysProperties.getInstance().addListener(modules); } } interface ConfigurationListener { void configurationChanged(ConfigurationEvent event); } interface PropertiesKeyListener { void configurationChanged(ConfigurationEvent event, String key, String value); } class ConfigurationEvent{ private EventType type; private String modules; public ConfigurationEvent(Object source, EventType type) { this.type = type; } public EventType getType() { return type; } public void setType(EventType type) { this.type = type; } public String getModules() { return modules; } public void setModules(String modules) { this.modules = modules; } } class ModulesListener { private String name; private List<ConfigurationListener> configurationListeners = new ArrayList<ConfigurationListener>(); private Map<String, PropertiesKeyListener> keyListeners = new HashMap<String, PropertiesKeyListener>(); public ModulesListener(String name) { this.name = name; } public String getName() { return name; } /** * 新增模块更新监听 * * @param listener 监听接口 */ public void addConfigurationListener(ConfigurationListener listener) { configurationListeners.add(listener); } /** * 新增Properties模块key更新监听 * @param key 配置项 * @param listener 监听接口 */ public void addKeyListener(String key, PropertiesKeyListener listener) { keyListeners.put(key, listener); } /** * 模块更新监听，动作执行 * * @param event */ public void actionConfigurationListener(ConfigurationEvent event) { for (ConfigurationListener listener : configurationListeners) { listener.configurationChanged(event); } } /** * Properties模块key更新监听，动作执行 * * @param event * @param key * @param value */ public void actionKeyListeners(ConfigurationEvent event, String key, String value) { if (keyListeners.containsKey(key)) { keyListeners.get(key).configurationChanged(event, key, value); } } } enum EventType { ADD, UPDATE, CLEAR; } import java.io.File; import java.io.FileInputStream; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Properties; /** * 读取实时的配置文件信息 */ public class SysProperties { private Map<String, Long> lastModifMap = new HashMap<String, Long>(); private static SysProperties instance; private Map<String, ModulesListener> modulesListeners = new HashMap<String, ModulesListener>(); public static SysProperties getInstance() { if (instance == null) { instance = new SysProperties(); } return instance; } public void addListener(List<ModulesListener> modules) { for(ModulesListener listener:modules){ modulesListeners.put(listener.getName(), listener); } } /** * @description 私有构造器启动一个线程实时监控配置文件 */ public SysProperties() { // 循环监控配置文件的变化，一旦发现文件发生变化了则重读配置文件 Thread t = new Thread() { public void run() { while (true) { // 间隔1秒 try { Thread.sleep(1000); } catch (InterruptedException e) { } try { String path = SysProperties.class.getClass().getResource("/config").getPath(); File[] tmps = new File(path).listFiles(); //File[] tmps = new File("E:\\Projects\\JavaProjects\\demo\\src\\main\\resources\\config").listFiles(); for (File file : tmps) { if (file.exists()) { long l = file.lastModified(); // this can also throw a SecurityException String fileAbsPath = file.getAbsolutePath(); long lastModif = getLastModif(fileAbsPath); if (l > lastModif) { // however, if we reached this point this recordLastModify(fileAbsPath, l); ConfigurationEvent event = null; //不知道删除事件 if(lastModif == 0){ event = new ConfigurationEvent(file.getName(), EventType.ADD); }else{ event = new ConfigurationEvent(file.getName(), EventType.UPDATE); } event.setModules(file.getName()); //无法精确key的变化 if(modulesListeners.containsKey(file.getName())){ ModulesListener listener = modulesListeners.get(file.getName()); Properties properties = transTo(file); listener.actionConfigurationListener(event); listener.actionKeyListeners(event, "name", properties.getProperty("name")); } } } } } catch (Exception e) { e.printStackTrace(); } } } }; t.start(); } private long getLastModif(String key) { long lastModif = 0; if (lastModifMap.get(key) != null) { lastModif = lastModifMap.get(key).longValue(); } return lastModif; } private void recordLastModify(String key, Long lastModif) { lastModifMap.put(key, lastModif); } public Properties transTo(File propertyFile){ Properties properties = new Properties(); FileInputStream inputStreamLocal = null; try { inputStreamLocal = new FileInputStream(propertyFile); properties.load(inputStreamLocal); return properties; }catch(Exception e){ e.printStackTrace(); } return properties; } }