statementutil.java

办公自动化项目

package hong.javanet.dao;

import java.sql.*;
import java.util.*;
import org.apache.log4j.Logger;

/**
 *
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2006</p>
 * <p>Company: </p>
 * @author 洪桃李
 * @version 1.0
 */
public class StatementUtil {
  private static Logger log = Logger.getLogger(StatementUtil.class);
  /**
   * 所有连接的缓存语句集合的集合
   */
  private static Map sessions = new HashMap();
  /**
   * 取得连接的缓存语句集合
   * @param conn Connection
   * @return Map
   */
  private static Map getStatementCaches(Connection conn) {
    Map statementCaches = (Map) sessions.get(conn);
    if (statementCaches == null) {
      statementCaches = new HashMap();
      sessions.put(conn, statementCaches);
    }
    return statementCaches;
  }

  /**
   * 清除连接的缓存语句集合
   * @param conn Connection
   * @throws SQLException
   */
  public static void clearStatementCaches(Connection conn) throws SQLException {
    Map statementCaches = (Map) sessions.get(conn);
    if (statementCaches != null) {
      sessions.remove(conn);
      Iterator iter = statementCaches.entrySet().iterator();
      while (iter.hasNext()) {
        try {
          Map.Entry item = (Map.Entry) iter.next();
          Statement stat = (Statement) item.getValue();
          stat.close();
        }
        catch (SQLException ex) {
          log.fatal(ex.getMessage(), ex);
        }
      }
    }
  }

  /**
   * 创建语句
   * @throws SQLException
   * @return Statement
   */
  public static Statement createStatement() throws SQLException {
    Connection conn = ConnectionUtil.currentConnection();
    Map statementCaches = getStatementCaches(conn);
    Statement stat = (Statement) statementCaches.get("");
    if (stat == null) {
      stat = conn.createStatement(
          ResultSet.TYPE_SCROLL_SENSITIVE,
          ResultSet.CONCUR_READ_ONLY);
      statementCaches.put("", stat);
    }
    return stat;

  }

  /**
   * 获得当前连接的某个预编译的语句
   * @param sql String
   * @throws SQLException
   * @return PreparedStatement
   */
  public static PreparedStatement prepareStatement(String sql) throws
      SQLException {
    Connection conn = ConnectionUtil.currentConnection();
    Map statementCaches = getStatementCaches(conn);
    PreparedStatement stat = (PreparedStatement) statementCaches.get(sql);
    if (stat == null) {
      stat = conn.prepareStatement(sql,
          ResultSet.TYPE_SCROLL_SENSITIVE,
          ResultSet.CONCUR_READ_ONLY);
      statementCaches.put(sql, stat);
    }
    return stat;
  }

  /**
   * 获得当前连接的某个可调用的语句
   * @param sql String
   * @throws SQLException
   * @return CallableStatement
   */
  public static CallableStatement prepareCall(String sql) throws SQLException {
    Connection conn = ConnectionUtil.currentConnection();
    Map statementCaches = getStatementCaches(conn);
    CallableStatement stat = (CallableStatement) statementCaches.get(sql);
    if (stat == null) {
      stat = conn.prepareCall(sql,
                              ResultSet.TYPE_SCROLL_SENSITIVE,
                              ResultSet.CONCUR_READ_ONLY);
      statementCaches.put(sql, stat);
    }
    return stat;
  }
}