nl.topicus.jdbc.MetaDataStore Maven / Gradle / Ivy

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package nl.topicus.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * Class for storing meta data needed for translating SQL statements into Cloud Spanner mutations,
 * such as key columns and their ordinal positions
 * 
 * @author loite
 *
 */
public class MetaDataStore {
  /**
   * Class for storing the primary key columns of a table in the correct order.
   * 
   * @author loite
   *
   */
  public class TableKeyMetaData {
    private final String name;

    private final List keyColumns = new ArrayList<>(2);

    TableKeyMetaData(String name) {
      this.name = name;
    }

    public List getKeyColumns() {
      return keyColumns;
    }

    @Override
    public boolean equals(Object o) {
      if (!(o instanceof TableKeyMetaData))
        return false;
      TableKeyMetaData other = (TableKeyMetaData) o;
      return Objects.equals(this.name, other.name);
    }

    @Override
    public int hashCode() {
      return name.hashCode();
    }
  }

  private final Connection connection;

  private final Map tables = new HashMap<>();

  MetaDataStore(Connection connection) {
    this.connection = connection;
  }

  public TableKeyMetaData getTable(String name) throws SQLException {
    if (name == null)
      return null;
    TableKeyMetaData res = tables.get(name.toUpperCase());
    if (res == null) {
      res = initTable(name);
      tables.put(name.toUpperCase(), res);
    }
    return res;
  }

  private TableKeyMetaData initTable(String name) throws SQLException {
    TableKeyMetaData table = new TableKeyMetaData(name);
    try (ResultSet rs = connection.getMetaData().getPrimaryKeys(null, null, name)) {
      while (rs.next()) {
        table.keyColumns.add(rs.getString("COLUMN_NAME").toUpperCase());
      }
    }
    return table;
  }

  void clear() {
    tables.clear();
  }

  void clearTable(String name) {
    if (name == null)
      return;
    tables.remove(name.toUpperCase());
  }

}