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HotRod is an ORM for Java, Spring and SpringBoot.
There is a newer version: 4.8.1
package org.hotrod.runtime.livesql.dialects;

import java.util.List;

import org.hotrod.runtime.livesql.exceptions.InvalidLiveSQLStatementException;
import org.hotrod.runtime.livesql.exceptions.UnsupportedLiveSQLFeatureException;
import org.hotrod.runtime.livesql.expressions.numbers.NumberExpression;
import org.hotrod.runtime.livesql.expressions.strings.StringExpression;
import org.hotrod.runtime.livesql.ordering.OrderingTerm;
import org.hotrod.runtime.livesql.queries.select.CrossJoin;
import org.hotrod.runtime.livesql.queries.select.FullOuterJoin;
import org.hotrod.runtime.livesql.queries.select.InnerJoin;
import org.hotrod.runtime.livesql.queries.select.Join;
import org.hotrod.runtime.livesql.queries.select.LeftOuterJoin;
import org.hotrod.runtime.livesql.queries.select.NaturalFullOuterJoin;
import org.hotrod.runtime.livesql.queries.select.NaturalInnerJoin;
import org.hotrod.runtime.livesql.queries.select.NaturalLeftOuterJoin;
import org.hotrod.runtime.livesql.queries.select.NaturalRightOuterJoin;
import org.hotrod.runtime.livesql.queries.select.QueryWriter;
import org.hotrod.runtime.livesql.queries.select.RightOuterJoin;
import org.hotrod.runtime.livesql.queries.select.UnionJoin;
import org.hotrodorm.hotrod.utils.Separator;

public class DB2Dialect extends SQLDialect {

  public DB2Dialect(final String productName, final String productVersion, final int majorVersion,
      final int minorVersion) {
    super(productName, productVersion, majorVersion, minorVersion);
  }

  // Identifier rendering

  @Override
  public IdentifierRenderer getIdentifierRenderer() {
    // Identifier names are by default upper case in DB2
    return new IdentifierRenderer("[A-Z][A-Z0-9_]*", "\"", "\"", false);
  }

  // Join rendering

  @Override
  public JoinRenderer getJoinRenderer() {
    return new JoinRenderer() {

      @Override
      public String renderJoinKeywords(final Join join) throws UnsupportedLiveSQLFeatureException {
        if (join instanceof InnerJoin) {
          return "JOIN";
        } else if (join instanceof LeftOuterJoin) {
          return "LEFT OUTER JOIN";
        } else if (join instanceof RightOuterJoin) {
          return "RIGHT OUTER JOIN";
        } else if (join instanceof FullOuterJoin) {
          return "FULL OUTER JOIN";
        } else if (join instanceof CrossJoin) {
          return "CROSS JOIN";
        } else if (join instanceof NaturalInnerJoin) {
          return "NATURAL JOIN";
        } else if (join instanceof NaturalLeftOuterJoin) {
          return "NATURAL LEFT OUTER JOIN";
        } else if (join instanceof NaturalRightOuterJoin) {
          return "NATURAL RIGHT OUTER JOIN";
        } else if (join instanceof NaturalFullOuterJoin) {
          return "NATURAL FULL OUTER JOIN";
        } else if (join instanceof UnionJoin) {
          throw new UnsupportedLiveSQLFeatureException("Union joins are not supported in DB2 database");
        } else {
          throw new UnsupportedLiveSQLFeatureException(
              "Invalid join type (" + join.getClass().getSimpleName() + ") in DB2 database");
        }
      }

    };
  }

  // Pagination rendering

  public PaginationRenderer getPaginationRenderer() {
    return new PaginationRenderer() {

      @Override
      public PaginationType getPaginationType(final Integer offset, final Integer limit) {
        if (offset != null) {
          if (!versionIsAtLeast(11, 1)) {
            throw new UnsupportedLiveSQLFeatureException("This version of DB2 (" + renderVersion()
                + ") does not support the OFFSET clause. DB2 versions 11.1 and newer do");
          }
        }
        return PaginationType.BOTTOM;
      }

      @Override
      public void renderTopPagination(final Integer offset, final Integer limit, final QueryWriter w) {
        throw new UnsupportedLiveSQLFeatureException("In DB2 pagination cannot be rendered at the top");
      }

      @Override
      public void renderBottomPagination(final Integer offset, final Integer limit, final QueryWriter w) {
        if (offset != null) {
          if (!versionIsAtLeast(11, 1)) {
            throw new UnsupportedLiveSQLFeatureException("This version of DB2 (" + renderVersion()
                + ") does not support the OFFSET clause. Support starts in DB2 11.1");
          }
        }
        if (offset != null) {
          w.write("\nOFFSET " + offset + " ROWS");
        }
        if (limit != null) {
          w.write("\nFETCH NEXT " + limit + " ROWS ONLY");
        }
      }

      @Override
      public void renderBeginEnclosingPagination(final Integer offset, final Integer limit, final QueryWriter w) {
        throw new UnsupportedLiveSQLFeatureException("In DB2 pagination cannot be rendered in an enclosing way");
      }

      @Override
      public void renderEndEnclosingPagination(final Integer offset, final Integer limit, final QueryWriter w) {
        throw new UnsupportedLiveSQLFeatureException("In DB2 pagination cannot be rendered in an enclosing way");
      }

    };
  }

  // Set operation rendering

  @Override
  public SetOperationRenderer getSetOperationRenderer() {
    return new SetOperationRenderer() {

      @Override
      public void render(final SetOperation setOperation, final QueryWriter w) {
        switch (setOperation) {
        case UNION:
          w.write("UNION");
          break;
        case UNION_ALL:
          w.write("UNION ALL");
          break;
        case INTERSECT:
          w.write("INTERSECT");
          break;
        case INTERSECT_ALL:
          w.write("INTERSECT ALL");
          break;
        case EXCEPT:
          w.write("EXCEPT");
          break;
        case EXCEPT_ALL:
          w.write("EXCEPT ALL");
          break;
        default:
          throw new InvalidLiveSQLStatementException("Invalid set operation '" + setOperation + "'.");
        }
      }

    };
  }

  // Function rendering

  @Override
  public FunctionRenderer getFunctionRenderer() {
    return new FunctionRenderer() {

      // General purpose functions

      @Override
      public void groupConcat(final QueryWriter w, final boolean distinct, final StringExpression value,
          final List ordering, final StringExpression separator) {
        if (distinct) {
          throw new UnsupportedLiveSQLFeatureException(
              "DB2 does not support DISTINCT on the GROUP_CONCAT() function (listagg())");
        }
        w.write("listagg(");
        value.renderTo(w);
        if (separator != null) {
          w.write(", ");
          separator.renderTo(w);
        }
        w.write(")");
        if (ordering != null && !ordering.isEmpty()) {
          w.write(" withing group (ORDER BY ");
          Separator sep = new Separator();
          for (OrderingTerm t : ordering) {
            w.write(sep.render());
            t.renderTo(w);
          }
          w.write(")");
        }
      }

      // Arithmetic functions

      @Override
      public void logarithm(final QueryWriter w, final NumberExpression x, final NumberExpression base) {
        if (base == null) {
          this.write(w, "ln", x);
        } else {
          w.write("(");
          this.write(w, "ln", x);
          w.write(" / ");
          this.write(w, "ln", base);
          w.write(")");
        }
      }

      // String functions

      // Date/Time functions

      @Override
      public void currentDate(final QueryWriter w) {
        w.write("current date");
      }

      @Override
      public void currentTime(final QueryWriter w) {
        w.write("current time");
      }

      @Override
      public void currentDateTime(final QueryWriter w) {
        w.write("current timestamp");
      }

    };
  }

}