Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)
ParameterHandler (getParameterObject, setParameters)
ResultSetHandler (handleResultSets, handleOutputParameters)
StatementHandler (prepare, parameterize, batch, update, query)

/* org.apache.ibatis.session.Configuration類中方法 */
public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
  ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
  /* 攔截ParameterHandler*/
  parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
  return parameterHandler;
}
public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, RowBounds rowBounds, ParameterHandler parameterHandler,
   ResultHandler resultHandler, BoundSql boundSql) {
  ResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, mappedStatement, parameterHandler, resultHandler, boundSql, rowBounds);
  /* 攔截ResultSetHandler*/
  resultSetHandler = (ResultSetHandler) interceptorChain.pluginAll(resultSetHandler);
  return resultSetHandler;
}
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
   /* 攔截StatementHandler*/
  statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
  return statementHandler;
}
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
 executorType = executorType == null ? defaultExecutorType : executorType;
 executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
 Executor executor;
 if (ExecutorType.BATCH == executorType) {
  executor = new BatchExecutor(this, transaction);
 } else if (ExecutorType.REUSE == executorType) {
  executor = new ReuseExecutor(this, transaction);
 } else {
  executor = new SimpleExecutor(this, transaction);
 }
 if (cacheEnabled) {
  executor = new CachingExecutor(executor);
 }
  /* 攔截Executor*/
 executor = (Executor) interceptorChain.pluginAll(executor);
 return executor;
}

/* 注解表明要攔截哪個(gè)接口的方法及其參數(shù) */
@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
public class YourInterceptor implements Interceptor{
 public Object intercept(Invocation invocation) throws Throwable{
  doSomeThing();
  /* 注：此處實(shí)際上使用Invocation.proceed()方法完成interceptorChain鏈的遍歷調(diào)用(即執(zhí)行所有注冊(cè)的Interceptor的intercept方法)，到最終被代理對(duì)象的原始方法調(diào)用 */
  return invocation.proceed();
 }
  /*生成成對(duì)目標(biāo)target的代理，而@Intercepts的注解是在Plugin.wrap中用到*/
 @Override
 public Object plugin(Object target){
   /* 當(dāng)目標(biāo)類是StatementHandler類型時(shí)，才包裝目標(biāo)類，不做無(wú)意義的代理 */
  return (target instanceof StatementHandler)?Plugin.wrap(target, this):target;
 }
  /*用于設(shè)置自定義的攔截器配置參數(shù)*/
 @Override
 public void setProperties(Properties properties){
 }
}

/* org.apache.ibatis.plugin.Plugin類 */
public class Plugin implements InvocationHandler {
 /* 省略代碼... */
 public static Object wrap(Object target, Interceptor interceptor) {
  /* 此處即為獲取Interceptor的注解簽名 */
  Map<Class<?>, Set<Method>> signatureMap = getSignatureMap(interceptor);
  Class<?> type = target.getClass();
  /* 獲取攔截目標(biāo)類相匹配的接口 */
  Class<?>[] interfaces = getAllInterfaces(type, signatureMap);
  if (interfaces.length > 0) {
   /* 使用jdk動(dòng)態(tài)代理 */
   return Proxy.newProxyInstance(type.getClassLoader(), interfaces, new Plugin(target, interceptor, signatureMap));
  }
  return target;
 }
 /* 攔截目標(biāo)類的所有方法的執(zhí)行都會(huì)變?yōu)樵诖藞?zhí)行 */
 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  try {
   Set<Method> methods = signatureMap.get(method.getDeclaringClass());
   if (methods != null && methods.contains(method)) {
    /* 執(zhí)行攔截器方法 */
    return interceptor.intercept(new Invocation(target, method, args));
   }
   return method.invoke(target, args);
  } catch (Exception e) {
   throw ExceptionUtil.unwrapThrowable(e);
  }
 }
 /* 省略代碼... */
}