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;    }}