resultset.java

关系型数据库 Postgresql 6.5.2

package postgresql;

import java.lang.*;
import java.io.*;
import java.math.*;
import java.text.*;
import java.util.*;
import java.sql.*;
import postgresql.largeobject.*;
import postgresql.util.*;

/**
 * This class implements the common internal methods used by both JDBC 1 and
 * JDBC 2 specifications.
 */
public abstract class ResultSet
{
  protected Vector rows;			// The results
  protected Field fields[];		// The field descriptions
  protected String status;		// Status of the result
  protected int updateCount;		// How many rows did we get back?
  protected int current_row;		// Our pointer to where we are at
  protected byte[][] this_row;		// the current row result
  protected Connection connection;	// the connection which we returned from
  protected SQLWarning warnings = null;	// The warning chain
  protected boolean wasNullFlag = false;	// the flag for wasNull()
  
  //  We can chain multiple resultSets together - this points to
  // next resultSet in the chain.
  protected ResultSet next = null;
  
  /**
   * Create a new ResultSet - Note that we create ResultSets to
   * represent the results of everything.
   *
   * @param fields an array of Field objects (basically, the
   *	ResultSet MetaData)
   * @param tuples Vector of the actual data
   * @param status the status string returned from the back end
   * @param updateCount the number of rows affected by the operation
   * @param cursor the positioned update/delete cursor name
   */
  public ResultSet(Connection conn, Field[] fields, Vector tuples, String status, int updateCount)
  {
    this.connection = conn;
    this.fields = fields;
    this.rows = tuples;
    this.status = status;
    this.updateCount = updateCount;
    this.this_row = null;
    this.current_row = -1;
  }
    
  /**
   * We at times need to know if the resultSet we are working
   * with is the result of an UPDATE, DELETE or INSERT (in which
   * case, we only have a row count), or of a SELECT operation
   * (in which case, we have multiple fields) - this routine
   * tells us.
   *
   * @return true if we have tuples available
   */
  public boolean reallyResultSet()
  {
    return (fields != null);
  }
  
  /**
   * Since ResultSets can be chained, we need some method of
   * finding the next one in the chain.  The method getNext()
   * returns the next one in the chain.
   *
   * @return the next ResultSet, or null if there are none
   */
  public java.sql.ResultSet getNext()
  {
    return (java.sql.ResultSet)next;
  }
  
  /**
   * This following method allows us to add a ResultSet object
   * to the end of the current chain.
   *
   * @param r the resultset to add to the end of the chain.
   */
  public void append(ResultSet r)
  {
    if (next == null)
      next = r;
    else
      next.append(r);
  }
  
  /**
   * If we are just a place holder for results, we still need
   * to get an updateCount.  This method returns it.
   *
   * @return the updateCount
   */
  public int getResultCount()
  {
    return updateCount;
  }
  
  /**
   * We also need to provide a couple of auxiliary functions for
   * the implementation of the ResultMetaData functions.  In
   * particular, we need to know the number of rows and the
   * number of columns.  Rows are also known as Tuples
   *
   * @return the number of rows
   */
  public int getTupleCount()
  {
    return rows.size();
  }
  
  /**
   * getColumnCount returns the number of columns
   *
   * @return the number of columns
   */
  public int getColumnCount()
  {
    return fields.length;
  }
   
   /**
    * Returns the status message from the backend.<p>
    * It is used internally by the driver.
    *
    * @return the status string from the backend
    */
   public String getStatusString()
   {
     return status;
   }
   
   /**
    * returns the OID of a field.<p>
    * It is used internally by the driver.
    *
    * @param field field id
    * @return the oid of that field's type
    */
   public int getColumnOID(int field)
   {
     return fields[field-1].getOID();
   }
  
    /**
     * This is part of the JDBC API, but is required by postgresql.Field
     */
    public abstract void close() throws SQLException;
    public abstract boolean next() throws SQLException;
    public abstract String getString(int i) throws SQLException;
}