odata2-jpa-processor/jpa-core/src/main/java/org/apache/olingo/odata2/jpa/processor/core/jpql/JPQLJoinSelectSingleStatementBuilder.java

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 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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package org.apache.olingo.odata2.jpa.processor.core.jpql;

import java.util.List;

import org.apache.olingo.odata2.jpa.processor.api.access.JPAJoinClause;
import org.apache.olingo.odata2.jpa.processor.api.exception.ODataJPARuntimeException;
import org.apache.olingo.odata2.jpa.processor.api.jpql.JPQLContextView;
import org.apache.olingo.odata2.jpa.processor.api.jpql.JPQLJoinSelectSingleContextView;
import org.apache.olingo.odata2.jpa.processor.api.jpql.JPQLStatement;
import org.apache.olingo.odata2.jpa.processor.api.jpql.JPQLStatement.JPQLStatementBuilder;

public class JPQLJoinSelectSingleStatementBuilder extends JPQLStatementBuilder {

  JPQLStatement jpqlStatement;
  private JPQLJoinSelectSingleContextView context;

  public JPQLJoinSelectSingleStatementBuilder(final JPQLContextView context) {
    this.context = (JPQLJoinSelectSingleContextView) context;
  }

  @Override
  public JPQLStatement build() throws ODataJPARuntimeException {
    jpqlStatement = createStatement(createJPQLQuery());
    this.context.setJPQLStatement(jpqlStatement.toString());
    return jpqlStatement;

  }

  private String createJPQLQuery() throws ODataJPARuntimeException {

    StringBuilder jpqlQuery = new StringBuilder();
    StringBuilder joinWhereCondition = null;

    jpqlQuery.append(JPQLStatement.KEYWORD.SELECT).append(JPQLStatement.DELIMITER.SPACE);
    jpqlQuery.append(context.getSelectExpression()).append(JPQLStatement.DELIMITER.SPACE);
    jpqlQuery.append(JPQLStatement.KEYWORD.FROM).append(JPQLStatement.DELIMITER.SPACE);

    if (context.getJPAJoinClauses() != null && !context.getJPAJoinClauses().isEmpty()) {
      List<JPAJoinClause> joinClauseList = context.getJPAJoinClauses();
      JPAJoinClause joinClause = joinClauseList.get(0);
      String joinCondition = joinClause.getJoinCondition();
      joinWhereCondition = new StringBuilder();
      if (joinCondition != null) {
        joinWhereCondition.append(joinCondition);
      }
      String relationShipAlias = null;
      joinClause = joinClauseList.get(1);
      jpqlQuery.append(joinClause.getEntityName()).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(joinClause.getEntityAlias());

      int i = 1;
      int limit = joinClauseList.size();
      relationShipAlias = joinClause.getEntityAlias();
      while (i < limit) {
        jpqlQuery.append(JPQLStatement.DELIMITER.SPACE);
        jpqlQuery.append(JPQLStatement.KEYWORD.JOIN).append(JPQLStatement.DELIMITER.SPACE);

        joinClause = joinClauseList.get(i);
        jpqlQuery.append(relationShipAlias).append(JPQLStatement.DELIMITER.PERIOD);
        jpqlQuery.append(joinClause.getEntityRelationShip()).append(JPQLStatement.DELIMITER.SPACE);
        jpqlQuery.append(joinClause.getEntityRelationShipAlias());

        relationShipAlias = joinClause.getEntityRelationShipAlias();
        i++;

        joinCondition = joinClause.getJoinCondition();
        if (joinCondition != null) {
          joinWhereCondition.append(JPQLStatement.DELIMITER.SPACE + JPQLStatement.Operator.AND
              + JPQLStatement.DELIMITER.SPACE);

          joinWhereCondition.append(joinCondition);
        }

      }
    } else {
      throw ODataJPARuntimeException.throwException(ODataJPARuntimeException.JOIN_CLAUSE_EXPECTED, null);
    }

    if (joinWhereCondition.length() > 0) {
      jpqlQuery.append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(JPQLStatement.KEYWORD.WHERE).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(joinWhereCondition.toString());
    }

    return jpqlQuery.toString();

  }

}