mybatis0121-mybatis拦截器执行流程-代理对象的执行

怼烎@ 2023-08-17 15:32 125阅读 0赞

1. MapperProxy的invoke(Object proxy, Method method, Object\[\] args)方法，也是jdk动态代理实现的，从mapper接口到sqlSession的跳跃

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      try {
        if (Object.class.equals(method.getDeclaringClass())) {
          return method.invoke(this, args);
        } else if (isDefaultMethod(method)) {
          return invokeDefaultMethod(proxy, method, args);
        }
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
      final MapperMethod mapperMethod = cachedMapperMethod(method);
      return mapperMethod.execute(sqlSession, args);
    }

2. MapperMethod的execute(SqlSession sqlSession, Object\[\] args)方法

public Object execute(SqlSession sqlSession, Object[] args) {
      Object result;
      switch (command.getType()) {
        case INSERT: {
        Object param = method.convertArgsToSqlCommandParam(args);
          result = rowCountResult(sqlSession.insert(command.getName(), param));
          break;
        }
        case UPDATE: {
          Object param = method.convertArgsToSqlCommandParam(args);
          // 因为我们的拦截是拦截的update方法，所以会执行这个
          result = rowCountResult(sqlSession.update(command.getName(), param));
          break;
        }
        case DELETE: {
          Object param = method.convertArgsToSqlCommandParam(args);
          result = rowCountResult(sqlSession.delete(command.getName(), param));
          break;
        }
        case SELECT:
          if (method.returnsVoid() && method.hasResultHandler()) {
            executeWithResultHandler(sqlSession, args);
            result = null;
          } else if (method.returnsMany()) {
            result = executeForMany(sqlSession, args);
          } else if (method.returnsMap()) {
            result = executeForMap(sqlSession, args);
          } else if (method.returnsCursor()) {
            result = executeForCursor(sqlSession, args);
          } else {
            Object param = method.convertArgsToSqlCommandParam(args);
            result = sqlSession.selectOne(command.getName(), param);
          }
          break;
        case FLUSH:
          result = sqlSession.flushStatements();
          break;
        default:
          throw new BindingException("Unknown execution method for: " + command.getName());
      }
      if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
        throw new BindingException("Mapper method '" + command.getName() 
            + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
      }
      return result;
    }

3. DefaultSqlSession的update(String statement, Object parameter)方法

public int update(String statement, Object parameter) {
      try {
        dirty = true;
        MappedStatement ms = configuration.getMappedStatement(statement);
        // 这边的executor对象被代理了，所以会进到InvocationHandler接口实现类的invoke方法中
        // 这里是进入到Plugin的invoke() 方法，ms, wrapCollection(parameter)就是args的封装
        return executor.update(ms, wrapCollection(parameter));
      } catch (Exception e) {
        throw ExceptionFactory.wrapException("Error updating database.  Cause: " + e, e);
      } finally {
        ErrorContext.instance().reset();
      }
    }

4. Plugin.invoke(Object proxy, Method method, Object\[\] args)方法，这是实现代理逻辑的地方

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      try {
          // 从拦截器签名中获取拦截方法
        Set<Method> methods = signatureMap.get(method.getDeclaringClass());
        // 如果当前方法在拦截方法集合中
        if (methods != null && methods.contains(method)) {
            // 执行拦截操作
            // target被拦截对象，一个拦截时是Executor对象
            // methon拦截方法
            // args 方法参数 args[0]是ms对象 args[1]是传入参数
          return interceptor.intercept(new Invocation(target, method, args));
        }
        return method.invoke(target, args);
      } catch (Exception e) {
        throw ExceptionUtil.unwrapThrowable(e);
      }
    }

5. interceptor.intercept(new Invocation(target, method, args))进入自定义拦截器

public Object intercept(Invocation invocation) throws Throwable {
        System.out.println("拦截器拦截");
        Object result = invocation.proceed();
        return result;
    }

6. 执行流程

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dyb25neWFv_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dyb25neWFv_size_16_color_FFFFFF_t_70]: /images/20230810/72f4bb4c7b17462e8806e18123d105d8.png