mybatis 实现 SQL 查询拦截修改详解

 public interface Interceptor {
 Object intercept(Invocation invocation) throws Throwable;
 Object plugin(Object target);
 void setProperties(Properties properties);
}

public class Plugin implements InvocationHandler {
 
 private Object target;
 private Interceptor interceptor;
 private Map, Set> signatureMap;
 
 private Plugin(Object target, Interceptor interceptor, Map, Set> signatureMap) {
  this.target = target;
  this.interceptor = interceptor;
  this.signatureMap = signatureMap;
 }
 
 public static Object wrap(Object target, Interceptor interceptor) {
  Map, Set> signatureMap = getSignatureMap(interceptor);
  Class type = target.getClass();
  Class[] interfaces = getAllInterfaces(type, signatureMap);
  if (interfaces.length > 0) {
   return Proxy.newProxyInstance(
     type.getClassLoader(),
     interfaces,
     new Plugin(target, interceptor, signatureMap));
  }
  return target;
 }
 
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  try {
   Set methods = signatureMap.get(method.getDeclaringClass());
   if (methods != null && methods.contains(method)) {
    return interceptor.intercept(new Invocation(target, method, args));
   }
   return method.invoke(target, args);
  } catch (Exception e) {
   throw ExceptionUtil.unwrapThrowable(e);
  }
 }
 
 private static Map, Set> getSignatureMap(Interceptor interceptor) {
  Intercepts interceptsAnnotation = interceptor.getClass().getAnnotation(Intercepts.class);
  if (interceptsAnnotation == null) { // issue #251
   throw new PluginException("No @Intercepts annotation was found in interceptor " + interceptor.getClass().getName());   
  }
  Signature[] sigs = interceptsAnnotation.value();
  Map, Set> signatureMap = new HashMap, Set>();
  for (Signature sig : sigs) {
   Set methods = signatureMap.get(sig.type());
   if (methods == null) {
    methods = new HashSet();
    signatureMap.put(sig.type(), methods);
   }
   try {
    Method method = sig.type().getMethod(sig.method(), sig.args());
    methods.add(method);
   } catch (NoSuchMethodException e) {
    throw new PluginException("Could not find method on " + sig.type() + " named " + sig.method() + ". Cause: " + e, e);
   }
  }
  return signatureMap;
 }
 
 private static Class[] getAllInterfaces(Class type, Map, Set> signatureMap) {
  Set> interfaces = new HashSet>();
  while (type != null) {
   for (Class c : type.getInterfaces()) {
    if (signatureMap.containsKey(c)) {
     interfaces.add(c);
    }
   }
   type = type.getSuperclass();
  }
  return interfaces.toArray(new Class[interfaces.size()]);
 }
 
}

@Intercepts({@Signature(method = "prepare", type = StatementHandler.class, args = {Connection.class}),
    @Signature(method = "query", type = StatementHandler.class, args = {java.sql.Statement.class, ResultHandler.class})})
public class TenantInterceptor implements Interceptor {
.....

  <!-- 配置mybatis -->
  <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="configLocation" value="classpath:mybatis/mybatis-config.xml"/>
    <!-- mapper扫描 -->
    <property name="mapperLocations" value="classpath:mybatis/*/*.xml"/>
    <property name="plugins">
      <array>
        <!-- 注册自己的拦截器 -->
        <bean id="paginationInterceptor" class="xxx.xxx.TenantInterceptor">
        </bean>
      </array>
    </property>
  </bean>