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/*
 * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
 * under one or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership. Camunda licenses this file to you under the Apache License,
 * Version 2.0; you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.camunda.bpm.engine.impl;

import static org.camunda.bpm.engine.impl.util.EnsureUtil.ensureNotNull;
import static org.camunda.bpm.engine.impl.util.EnsureUtil.ensureNull;

import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.camunda.bpm.engine.ProcessEngineException;
import org.camunda.bpm.engine.exception.NotValidException;
import org.camunda.bpm.engine.impl.QueryValidators.AdhocQueryValidator;
import org.camunda.bpm.engine.impl.context.Context;
import org.camunda.bpm.engine.impl.db.ListQueryParameterObject;
import org.camunda.bpm.engine.impl.interceptor.Command;
import org.camunda.bpm.engine.impl.interceptor.CommandContext;
import org.camunda.bpm.engine.impl.interceptor.CommandExecutor;
import org.camunda.bpm.engine.impl.util.ImmutablePair;
import org.camunda.bpm.engine.impl.util.QueryMaxResultsLimitUtil;
import org.camunda.bpm.engine.query.Query;
import org.camunda.bpm.engine.query.QueryProperty;
import org.joda.time.DateTime;


/**
 * Abstract superclass for all query types.
 *
 * @author Joram Barrez
 */
public abstract class AbstractQuery, U> extends ListQueryParameterObject implements Command, Query, Serializable {

  private static final long serialVersionUID = 1L;

  public static final String SORTORDER_ASC = "asc";
  public static final String SORTORDER_DESC = "desc";

  protected enum ResultType {
    LIST, LIST_PAGE, LIST_IDS, LIST_DEPLOYMENT_ID_MAPPINGS, SINGLE_RESULT, COUNT
  }
  protected transient CommandExecutor commandExecutor;

  protected ResultType resultType;

  protected Map expressions = new HashMap<>();

  protected Set>> validators = new HashSet<>();

  protected boolean maxResultsLimitEnabled;

  protected AbstractQuery() {
  }

  protected AbstractQuery(CommandExecutor commandExecutor) {
    this.commandExecutor = commandExecutor;

    // all queries that are created with a dedicated command executor
    // are treated as adhoc queries (i.e. queries not created in the context
    // of a command)
    addValidator(AdhocQueryValidator.>get());
  }

  public AbstractQuery setCommandExecutor(CommandExecutor commandExecutor) {
    this.commandExecutor = commandExecutor;
    return this;
  }

  public T orderBy(QueryProperty property) {
    return orderBy(new QueryOrderingProperty(null, property));
  }

  @SuppressWarnings("unchecked")
  public T orderBy(QueryOrderingProperty orderProperty) {
    this.orderingProperties.add(orderProperty);
    return (T) this;
  }

  public T asc() {
    return direction(Direction.ASCENDING);
  }

  public T desc() {
    return direction(Direction.DESCENDING);
  }

  @SuppressWarnings("unchecked")
  public T direction(Direction direction) {
    QueryOrderingProperty currentOrderingProperty = null;

    if (!orderingProperties.isEmpty()) {
      currentOrderingProperty = orderingProperties.get(orderingProperties.size() - 1);
    }

    ensureNotNull(NotValidException.class, "You should call any of the orderBy methods first before specifying a direction", "currentOrderingProperty", currentOrderingProperty);

    if (currentOrderingProperty.getDirection() != null) {
      ensureNull(NotValidException.class, "Invalid query: can specify only one direction desc() or asc() for an ordering constraint", "direction", direction);
    }

    currentOrderingProperty.setDirection(direction);
    return (T) this;
  }

  protected void checkQueryOk() {

    for (QueryOrderingProperty orderingProperty : orderingProperties) {
      ensureNotNull(NotValidException.class, "Invalid query: call asc() or desc() after using orderByXX()", "direction", orderingProperty.getDirection());
    }

  }

  @SuppressWarnings("unchecked")
  public U singleResult() {
    this.resultType = ResultType.SINGLE_RESULT;
    return (U) executeResult(resultType);
  }

  @SuppressWarnings("unchecked")
  public List list() {
    this.resultType = ResultType.LIST;
    return (List) executeResult(resultType);
  }

  @SuppressWarnings("unchecked")
  public List listPage(int firstResult, int maxResults) {
    this.firstResult = firstResult;
    this.maxResults = maxResults;
    this.resultType = ResultType.LIST_PAGE;
    return (List) executeResult(resultType);
  }

  public Object executeResult(ResultType resultType) {

    if (commandExecutor != null) {
      if (!maxResultsLimitEnabled) {
        maxResultsLimitEnabled = Context.getCommandContext() == null;
      }

      return commandExecutor.execute(this);
    }

    switch (resultType) {
      case SINGLE_RESULT:
        return executeSingleResult(Context.getCommandContext());
      case LIST_PAGE:
      case LIST:
        return evaluateExpressionsAndExecuteList(Context.getCommandContext(), null);
      default:
        throw new ProcessEngineException("Unknown result type!");
    }
  }

  public long count() {
    this.resultType = ResultType.COUNT;
    if (commandExecutor!=null) {
      return (Long) commandExecutor.execute(this);
    }
    return evaluateExpressionsAndExecuteCount(Context.getCommandContext());
  }

  @SuppressWarnings("unchecked")
  public List unlimitedList() {
    this.resultType = ResultType.LIST;
    if (commandExecutor != null) {
      return (List) commandExecutor.execute(this);
    }
    return evaluateExpressionsAndExecuteList(Context.getCommandContext(), null);
  }

  public Object execute(CommandContext commandContext) {
    if (resultType==ResultType.LIST) {
      return evaluateExpressionsAndExecuteList(commandContext, null);
    } else if (resultType==ResultType.SINGLE_RESULT) {
      return executeSingleResult(commandContext);
    } else if (resultType==ResultType.LIST_PAGE) {
      return evaluateExpressionsAndExecuteList(commandContext, null);
    } else if (resultType == ResultType.LIST_IDS) {
      return evaluateExpressionsAndExecuteIdsList(commandContext);
    } else if (resultType == ResultType.LIST_DEPLOYMENT_ID_MAPPINGS) {
      return evaluateExpressionsAndExecuteDeploymentIdMappingsList(commandContext);
    } else {
      return evaluateExpressionsAndExecuteCount(commandContext);
    }
  }

  public long evaluateExpressionsAndExecuteCount(CommandContext commandContext) {
    validate();
    evaluateExpressions();
    return !hasExcludingConditions() ? executeCount(commandContext) : 0l;
  }

  public abstract long executeCount(CommandContext commandContext);

  public List evaluateExpressionsAndExecuteList(CommandContext commandContext, Page page) {
    checkMaxResultsLimit();
    validate();
    evaluateExpressions();
    return !hasExcludingConditions() ? executeList(commandContext, page) : new ArrayList<>();
  }

  /**
   * Whether or not the query has excluding conditions. If the query has excluding conditions,
   * (e.g. task due date before and after are excluding), the SQL query is avoided and a default result is
   * returned. The returned result is the same as if the SQL was executed and there were no entries.
   *
   * @return {@code true} if the query does have excluding conditions, {@code false} otherwise
   */
  protected boolean hasExcludingConditions() {
    return false;
  }

  /**
   * Executes the actual query to retrieve the list of results.
   * @param page used if the results must be paged. If null, no paging will be applied.
   */
  public abstract List executeList(CommandContext commandContext, Page page);

  public U executeSingleResult(CommandContext commandContext) {
    disableMaxResultsLimit();
    List results = evaluateExpressionsAndExecuteList(commandContext, new Page(0, 2));
    if (results.size() == 1) {
      return results.get(0);
    } else if (results.size() > 1) {
     throw new ProcessEngineException("Query return "+results.size()+" results instead of max 1");
    }
    return null;
  }

  public Map getExpressions() {
    return expressions;
  }

  public void setExpressions(Map expressions) {
    this.expressions = expressions;
  }

  public void addExpression(String key, String expression) {
    this.expressions.put(key, expression);
  }

  protected void evaluateExpressions() {
    // we cannot iterate directly on the entry set cause the expressions
    // are removed by the setter methods during the iteration
    ArrayList> entries = new ArrayList<>(expressions.entrySet());

    for (Map.Entry entry : entries) {
      String methodName = entry.getKey();
      String expression = entry.getValue();

      Object value;

      try {
        value = Context.getProcessEngineConfiguration()
          .getExpressionManager()
          .createExpression(expression)
          .getValue(null);
      }
      catch (ProcessEngineException e) {
        throw new ProcessEngineException("Unable to resolve expression '" + expression + "' for method '" + methodName + "' on class '" + getClass().getCanonicalName() + "'", e);
      }

      // automatically convert DateTime to date
      if (value instanceof DateTime) {
        value = ((DateTime) value).toDate();
      }

      try {
        Method method = getMethod(methodName);
        method.invoke(this, value);
      } catch (InvocationTargetException e) {
        throw new ProcessEngineException("Unable to invoke method '" + methodName + "' on class '" + getClass().getCanonicalName() + "'", e);
      } catch (IllegalAccessException e) {
        throw new ProcessEngineException("Unable to access method '" + methodName + "' on class '" + getClass().getCanonicalName() + "'", e);
      }
    }
  }

  protected Method getMethod(String methodName) {
    for (Method method : getClass().getDeclaredMethods()) {
      if (method.getName().equals(methodName)) {
        return method;
      }
    }
    throw new ProcessEngineException("Unable to find method '" + methodName + "' on class '" + getClass().getCanonicalName() + "'");
  }

  public T extend(T extendingQuery) {
    throw new ProcessEngineException("Extending of query type '" + extendingQuery.getClass().getCanonicalName() + "' currently not supported");
  }

  protected void mergeOrdering(AbstractQuery extendedQuery, AbstractQuery extendingQuery) {
    extendedQuery.orderingProperties = this.orderingProperties;
    if (extendingQuery.orderingProperties != null) {
       if (extendedQuery.orderingProperties == null) {
         extendedQuery.orderingProperties = extendingQuery.orderingProperties;
       }
       else {
         extendedQuery.orderingProperties.addAll(extendingQuery.orderingProperties);
       }
    }
  }

  protected void mergeExpressions(AbstractQuery extendedQuery, AbstractQuery extendingQuery) {
    Map mergedExpressions = new HashMap<>(extendingQuery.getExpressions());
    for (Map.Entry entry : this.getExpressions().entrySet()) {
      if (!mergedExpressions.containsKey(entry.getKey())) {
        mergedExpressions.put(entry.getKey(), entry.getValue());
      }
    }
    extendedQuery.setExpressions(mergedExpressions);
  }

  public void validate() {
    for (Validator> validator : validators) {
      validate(validator);
    }
  }

  public void validate(Validator> validator) {
    validator.validate(this);
  }

  public void addValidator(Validator> validator) {
    validators.add(validator);
  }

  public void removeValidator(Validator> validator) {
    validators.remove(validator);
  }

  @SuppressWarnings("unchecked")
  public List listIds() {
    this.resultType = ResultType.LIST_IDS;
    List ids = null;
    if (commandExecutor != null) {
      ids = (List) commandExecutor.execute(this);
    } else {
      ids = evaluateExpressionsAndExecuteIdsList(Context.getCommandContext());
    }

    if (ids != null) {
      QueryMaxResultsLimitUtil.checkMaxResultsLimit(ids.size());
    }

    return ids;
  }

  @SuppressWarnings("unchecked")
  public List> listDeploymentIdMappings() {
    this.resultType = ResultType.LIST_DEPLOYMENT_ID_MAPPINGS;
    List> ids = null;
    if (commandExecutor != null) {
      ids = (List>) commandExecutor.execute(this);
    } else {
      ids = evaluateExpressionsAndExecuteDeploymentIdMappingsList(Context.getCommandContext());
    }

    if (ids != null) {
      QueryMaxResultsLimitUtil.checkMaxResultsLimit(ids.size());
    }

    return ids;
  }

  public List evaluateExpressionsAndExecuteIdsList(CommandContext commandContext) {
    validate();
    evaluateExpressions();
    return !hasExcludingConditions() ? executeIdsList(commandContext) : new ArrayList<>();
  }

  public List executeIdsList(CommandContext commandContext) {
    throw new UnsupportedOperationException("executeIdsList not supported by " + getClass().getCanonicalName());
  }

  public List> evaluateExpressionsAndExecuteDeploymentIdMappingsList(CommandContext commandContext) {
    validate();
    evaluateExpressions();
    return !hasExcludingConditions() ? executeDeploymentIdMappingsList(commandContext) : new ArrayList<>();
  }

  public List> executeDeploymentIdMappingsList(CommandContext commandContext) {
    throw new UnsupportedOperationException("executeDeploymentIdMappingsList not supported by " + getClass().getCanonicalName());
  }

  protected void checkMaxResultsLimit() {
    if (maxResultsLimitEnabled) {
      QueryMaxResultsLimitUtil.checkMaxResultsLimit(maxResults);
    }
  }

  public void enableMaxResultsLimit() {
    maxResultsLimitEnabled = true;
  }

  public void disableMaxResultsLimit() {
    maxResultsLimitEnabled = false;
  }

}
 















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