97 lines
2.6 KiB
Dart
97 lines
2.6 KiB
Dart
/**
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责任链模式（Chain of Responsibility Pattern）
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意图：避免请求发送者与接收者耦合在一起，让多个对象都有可能接收请求，将这些对象连接成一条链，并且沿着这条链传递请求，直到有对象处理它为止。
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主要解决：职责链上的处理者负责处理请求，客户只需要将请求发送到职责链上即可，无须关心请求的处理细节和请求的传递，所以职责链将请求的发送者和请求的处理者解耦了。
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何时使用：在处理消息的时候以过滤很多道。
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如何解决：拦截的类都实现统一接口。
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*/
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main(List<String> args) {
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AbstractLogger loggerChain = LoggerFactory.getChainOfLoggers();
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loggerChain.logMessage(AbstractLogger.INFO, "This is an information.");
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loggerChain.logMessage(
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AbstractLogger.DEBUG, "This is a debug level information.");
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loggerChain.logMessage(AbstractLogger.ERROR, "This is an error information.");
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}
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//////////////////////////////////////////////////////////////////
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///
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/// 创建抽象的记录器类
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///
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abstract class AbstractLogger {
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static int INFO = 1;
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static int DEBUG = 2;
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static int ERROR = 3;
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int _level;
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//责任链中的下一个元素
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AbstractLogger _nextLogger;
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void setNextLogger(AbstractLogger nextLogger) {
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this._nextLogger = nextLogger;
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}
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void logMessage(int level, String message) {
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if (this._level <= level) {
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write(message);
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}
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if (_nextLogger != null) {
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_nextLogger.logMessage(level, message);
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}
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}
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void write(String message);
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}
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///
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/// 创建扩展了该记录器类的实体类
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///
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class ConsoleLogger extends AbstractLogger {
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ConsoleLogger(int level) {
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this._level = level;
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}
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@override
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void write(String message) {
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print("Standard Console::Logger: $message");
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}
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}
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class ErrorLogger extends AbstractLogger {
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ErrorLogger(int level) {
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this._level = level;
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}
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@override
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void write(String message) {
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print("Error Console::Logger: $message");
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}
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}
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class FileLogger extends AbstractLogger {
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FileLogger(int level) {
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this._level = level;
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}
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@override
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void write(String message) {
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print("File::Logger: $message");
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}
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}
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class LoggerFactory {
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static AbstractLogger getChainOfLoggers() {
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AbstractLogger errorLogger = new ErrorLogger(AbstractLogger.ERROR);
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AbstractLogger fileLogger = new FileLogger(AbstractLogger.DEBUG);
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AbstractLogger consoleLogger = new ConsoleLogger(AbstractLogger.INFO);
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errorLogger.setNextLogger(fileLogger);
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fileLogger.setNextLogger(consoleLogger);
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return errorLogger;
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}
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}
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