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设计模式-装饰模式 Java

news 2025/8/8 7:18:11

模式概述

装饰模式（Decorator Pattern）是一种结构型设计模式，它允许向一个现有对象动态添加新功能，同时又不改变其结构。这种模式创建了一个装饰类，用于包装原有的类，提供了比继承更有弹性的替代方案。

核心思想：通过组合而非继承的方式，在运行时动态地扩展对象功能，遵循"开闭原则"（对扩展开放，对修改关闭

简单代码示例

// 1. 抽象构件
interface DataSource {void writeData(String data);String readData();
}// 2. 具体构件
class FileDataSource implements DataSource {private String filename;public FileDataSource(String filename) {this.filename = filename;}@Overridepublic void writeData(String data) {System.out.println("Writing data to file: " + data);}@Overridepublic String readData() {return "Data from file";}
}// 3. 抽象装饰类
abstract class DataSourceDecorator implements DataSource {protected DataSource wrappee;public DataSourceDecorator(DataSource source) {this.wrappee = source;}
}// 4. 具体装饰类 - 加密装饰器
class EncryptionDecorator extends DataSourceDecorator {public EncryptionDecorator(DataSource source) {super(source);}@Overridepublic void writeData(String data) {String encrypted = encrypt(data);wrappee.writeData(encrypted);}@Overridepublic String readData() {String data = wrappee.readData();return decrypt(data);}private String encrypt(String data) {return "ENCRYPTED(" + data + ")";}private String decrypt(String data) {return data.replace("ENCRYPTED(", "").replace(")", "");}
}// 5. 具体装饰类 - 压缩装饰器
class CompressionDecorator extends DataSourceDecorator {public CompressionDecorator(DataSource source) {super(source);}@Overridepublic void writeData(String data) {String compressed = compress(data);wrappee.writeData(compressed);}@Overridepublic String readData() {String data = wrappee.readData();return decompress(data);}private String compress(String data) {return "COMPRESSED[" + data + "]";}private String decompress(String data) {return data.replace("COMPRESSED[", "").replace("]", "");}
}// 客户端代码
public class DecoratorDemo {public static void main(String[] args) {// 基本文件数据源DataSource source = new FileDataSource("data.txt");// 添加加密功能DataSource encryptedSource = new EncryptionDecorator(source);encryptedSource.writeData("Sensitive data");System.out.println("Read encrypted: " + encryptedSource.readData());// 添加压缩和加密功能DataSource secureSource = new CompressionDecorator(new EncryptionDecorator(source));secureSource.writeData("Large sensitive data");System.out.println("Read compressed & encrypted: " + secureSource.readData());}
}

技术细节

1.模式组成

组件	职责说明
抽象构件	定义对象接口，可以动态添加职责
具体构件	实现Component接口，定义要添加功能的对象
抽象装饰类	继承Component，维护一个Component对象的引用
具体装饰类	向构件添加具体职责

2.优缺点