DatabasePlatform.java

package com.avaje.ebean.config.dbplatform;

import java.sql.Types;

import javax.sql.DataSource;

import com.avaje.ebean.BackgroundExecutor;
import com.avaje.ebean.Query;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Database platform specific settings.
 */
public class DatabasePlatform {

  /** The Constant logger. */
  private static final Logger logger = LoggerFactory.getLogger(DatabasePlatform.class);

  /** The open quote used by quoted identifiers. */
  protected String openQuote = "\"";

  /** The close quote used by quoted identifiers. */
  protected String closeQuote = "\"";

  /** For limit/offset, row_number etc limiting of SQL queries. */
  protected SqlLimiter sqlLimiter = new LimitOffsetSqlLimiter();

  /** Mapping of JDBC to Database types. */
  protected DbTypeMap dbTypeMap = new DbTypeMap();

  /** DB specific DDL syntax. */
  protected DbDdlSyntax dbDdlSyntax = new DbDdlSyntax();

  /** Defines DB identity/sequence features. */
  protected DbIdentity dbIdentity = new DbIdentity();

  /** The JDBC type to map booleans to (by default). */
  protected int booleanDbType = Types.BOOLEAN;

  /** The JDBC type to map Blob to. */
  protected int blobDbType = Types.BLOB;

  /** The JDBC type to map Clob to. */
  protected int clobDbType = Types.CLOB;

  /** For Oracle treat empty strings as null. */
  protected boolean treatEmptyStringsAsNull;

  /** The name. */
  protected String name = "generic";

  /**
   * Use a BackTick ` at the beginning and end of table or column names that you
   * want to use quoted identifiers for. The backticks get converted to the
   * appropriate characters in convertQuotedIdentifiers
   */
  private static final char BACK_TICK = '`';

  protected DbEncrypt dbEncrypt;

  protected boolean idInExpandedForm;

  protected boolean selectCountWithAlias;

  /**
   * Instantiates a new database platform.
   */
  public DatabasePlatform() {
  }

  /**
   * Return the name of the DatabasePlatform.
   * <p>
   * "generic" is returned when no specific database platform has been set or
   * found.
   * </p>
   * 
   * @return the name
   */
  public String getName() {
    return name;
  }

  /**
   * Return a DB Sequence based IdGenerator.
   * 
   * @param be
   *          the BackgroundExecutor that can be used to load the sequence if
   *          desired
   * @param ds
   *          the DataSource
   * @param seqName
   *          the name of the sequence
   * @param batchSize
   *          the number of sequences that should be loaded
   */
  public IdGenerator createSequenceIdGenerator(BackgroundExecutor be, DataSource ds,
      String seqName, int batchSize) {

    return null;
  }

  /**
   * Return the DbEncrypt handler for this DB platform.
   */
  public DbEncrypt getDbEncrypt() {
    return dbEncrypt;
  }

  /**
   * Set the DbEncrypt handler for this DB platform.
   */
  public void setDbEncrypt(DbEncrypt dbEncrypt) {
    this.dbEncrypt = dbEncrypt;
  }

  /**
   * Return the mapping of JDBC to DB types.
   * 
   * @return the db type map
   */
  public DbTypeMap getDbTypeMap() {
    return dbTypeMap;
  }

  /**
   * Return the DDL syntax for this platform.
   * 
   * @return the db ddl syntax
   */
  public DbDdlSyntax getDbDdlSyntax() {
    return dbDdlSyntax;
  }

  /**
   * Return the close quote for quoted identifiers.
   * 
   * @return the close quote
   */
  public String getCloseQuote() {
    return closeQuote;
  }

  /**
   * Return the open quote for quoted identifiers.
   * 
   * @return the open quote
   */
  public String getOpenQuote() {
    return openQuote;
  }

  /**
   * Return the JDBC type used to store booleans.
   * 
   * @return the boolean db type
   */
  public int getBooleanDbType() {
    return booleanDbType;
  }

  /**
   * Return the data type that should be used for Blob.
   * <p>
   * This is typically Types.BLOB but for Postgres is Types.LONGVARBINARY for
   * example.
   * </p>
   */
  public int getBlobDbType() {
    return blobDbType;
  }

  /**
   * Return the data type that should be used for Clob.
   * <p>
   * This is typically Types.CLOB but for Postgres is Types.VARCHAR.
   * </p>
   */
  public int getClobDbType() {
    return clobDbType;
  }

  /**
   * Return true if empty strings should be treated as null.
   * 
   * @return true, if checks if is treat empty strings as null
   */
  public boolean isTreatEmptyStringsAsNull() {
    return treatEmptyStringsAsNull;
  }

  /**
   * Return true if a compound ID in (...) type expression needs to be in
   * expanded form of (a=? and b=?) or (a=? and b=?) or ... rather than (a,b) in
   * ((?,?),(?,?),...);
   */
  public boolean isIdInExpandedForm() {
    return idInExpandedForm;
  }

  /**
   * Return the DB identity/sequence features for this platform.
   * 
   * @return the db identity
   */
  public DbIdentity getDbIdentity() {
    return dbIdentity;
  }

  /**
   * Return the SqlLimiter used to apply additional sql around a query to limit
   * its results.
   * <p>
   * Basically add the clauses for limit/offset, rownum, row_number().
   * </p>
   * 
   * @return the sql limiter
   */
  public SqlLimiter getSqlLimiter() {
    return sqlLimiter;
  }

  /**
   * Convert backticks to the platform specific open quote and close quote
   * 
   * <p>
   * Specific plugins may implement this method to cater for platform specific
   * naming rules.
   * </p>
   * 
   * @param dbName
   *          the db name
   * 
   * @return the string
   */
  public String convertQuotedIdentifiers(String dbName) {
    // Ignore null values e.g. schema name or catalog
    if (dbName != null && dbName.length() > 0) {
      if (dbName.charAt(0) == BACK_TICK) {
        if (dbName.charAt(dbName.length() - 1) == BACK_TICK) {

          String quotedName = getOpenQuote();
          quotedName += dbName.substring(1, dbName.length() - 1);
          quotedName += getCloseQuote();

          return quotedName;

        } else {
          logger.error("Missing backquote on [" + dbName + "]");
        }
      }
    }
    return dbName;
  }

  /**
   * Set to true if select count against anonymous view requires an alias.
   */
  public boolean isSelectCountWithAlias() {
    return selectCountWithAlias;
  }

  public String completeSql(String sql, Query<?> query) {
    if (Boolean.TRUE.equals(query.isForUpdate())) {
      sql = withForUpdate(sql);
    }

    return sql;
  }

  protected String withForUpdate(String sql) {
    // silently assume the database does not support the "for update" clause.
    logger.info("it seems your database does not support the 'for update' clause");

    return sql;
  }
}