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 {
    @Override
    public 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();
    }

    @Override
    public 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

@Test
   public 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 {
    @Override
    public 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();
    }


    @Override
    public 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();
    }

    @Override
    public 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