代理模式实现缓存

静态代理

代理类在编译时就已经确定

创建数据查询接口

public interface DataQuery {String query(String queryKey);
}

创建被代理类

public class MySQLDataQuery implements DataQuery {@Overridepublic String query(String queryKey) {// 查询数据库并返回结果System.out.println("查询数据库:" + queryKey);return queryKey;}
}

创建代理类

public class MySQLDataQueryProxy implements DataQuery {private final DataQuery dataQuery;private final Map<String, String> cache = new HashMap<>(16);public MySQLDataQueryProxy() {this.dataQuery = new MySQLDataQuery();}@Overridepublic String query(String queryKey) {String result = cache.get(queryKey);if (result == null) {System.out.println("未命中缓存:" + queryKey);result = dataQuery.query(queryKey);cache.put(queryKey, result);System.out.println("已存入缓存:" + queryKey);} else {System.out.println("命中缓存:" + queryKey);}return result;}
}

测试代码

@Testpublic void testStatic() {DataQuery dataQuery = new MySQLDataQueryProxy();dataQuery.query("k1");System.out.println("--------------------------------");dataQuery.query("k1");System.out.println("--------------------------------");dataQuery.query("k2");System.out.println("--------------------------------");}

测试结果

未命中缓存:k1
查询数据库:k1
已存入缓存:k1

命中缓存:k1

未命中缓存:k2
查询数据库:k2
已存入缓存:k2

动态代理

动态代理是指代理类在运行时动态生成。

JDK动态代理

创建数据查询接口

public interface DataQuery {String query(String queryKey);
}

创建被代理类

public class MySQLDataQuery implements DataQuery {@Overridepublic String query(String queryKey) {// 查询数据库并返回结果System.out.println("JDK-查询数据库:" + queryKey);return queryKey;}
}

创建InvocationHandler接口的实现类

public class CacheInvocationHandler implements InvocationHandler {private DataQuery dataQuery;private Map<String, String> cache = new HashMap<>(1024);public CacheInvocationHandler() {dataQuery = new MySQLDataQuery();}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {String result = null;if ("query".equals(method.getName())) {result = cache.get(args[0].toString());if (result != null) {System.out.println("JDK-命中缓存:" + args[0].toString());return result;}System.out.println("JDK-未命中缓存:" + args[0].toString());result = (String) method.invoke(dataQuery, args);cache.put(args[0].toString(), result);System.out.println("JDK-已存入缓存:" + args[0].toString());return result;}return method.invoke(dataQuery, args);}
}

创建Proxy类的实例并测试

@Test
public void testJDK() {ClassLoader classLoader = TestProxy.class.getClassLoader();Class[] interfaces = new Class[]{DataQuery.class};InvocationHandler invocationHandler = new CacheInvocationHandler();DataQuery dataQuery = (DataQuery) Proxy.newProxyInstance(classLoader, interfaces, invocationHandler);dataQuery.query("k1");System.out.println("--------------------------------");dataQuery.query("k1");System.out.println("--------------------------------");dataQuery.query("k2");System.out.println("--------------------------------");
}

测试结果

JDK-未命中缓存:k1
JDK-查询数据库:k1
JDK-已存入缓存:k1

JDK-命中缓存:k1

JDK-未命中缓存:k2
JDK-查询数据库:k2
JDK-已存入缓存:k2

CGLIB动态代理

创建被代理类

public class MySQLDataQuery{public String query(String queryKey) {// 查询数据库并返回结果System.out.println("CGLIB-查询数据库:" + queryKey);return queryKey;}
}

创建MethodInterceptor接口的实现类

public class CacheMethodInterceptor implements MethodInterceptor {private HashMap<String, String> cache = new HashMap<>(16);private MySQLDataQuery dataQuery;public CacheMethodInterceptor() {this.dataQuery = new MySQLDataQuery();}@Overridepublic Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {String result = null;if ("query".equals(method.getName())) {result = cache.get(args[0].toString());if (result != null) {System.out.println("CGLIB-命中缓存:"+args[0].toString());return result;}System.out.println("CGLIB-未命中缓存:"+args[0].toString());result = (String) method.invoke(dataQuery, args);cache.put(args[0].toString(), result);System.out.println("CGLIB-已存入缓存:"+args[0].toString());return result;}return method.invoke(dataQuery, args);}
}

创建Enhancer类并测试

@Test
public void testCglib(){Enhancer enhancer = new Enhancer();enhancer.setSuperclass(MySQLDataQuery.class);enhancer.setCallback(new CacheMethodInterceptor());MySQLDataQuery dataQuery = (MySQLDataQuery)enhancer.create();dataQuery.query("k1");System.out.println();dataQuery.query("k1");System.out.println();dataQuery.query("k2");System.out.println();
}

测试结果

CGLIB-未命中缓存:k1
CGLIB-查询数据库:k1
CGLIB-已存入缓存:k1

CGLIB-命中缓存:k1

CGLIB-未命中缓存:k2
CGLIB-查询数据库:k2
CGLIB-已存入缓存:k2