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发信人: Lg (创造人生的传奇), 信区: Java
标  题: DBHandler -- 0.1
发信站: 荔园晨风BBS站 (Thu Jul  5 17:12:24 2001) , 转信

DBHandler的0.1版本，主要是配置文档的剖析，程序的整体结构。

package jdbc_study;

/**
* Title:        JDBC Study
* Description:
* Copyright:    Copyright (c) 2001
* Company:      Vista
* @author Gang Liu
* @version 1.0
*/
import java.util.*;
import java.io.*;
import java.sql.*;

import org.apache.log4j.*;

import vista.sql.*;

import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

public final class DBHandler {

  private static Category cat = Category.getInstance(DBHandler.class.getName());

  private static boolean firstInstance = true;

  private static Hashtable configuration = null;

  private String poolName = null;

  private String handlerID = null;

  private String querySQL = null;

  private DBConnectionManager dbConnM = null;

  private Connection conn = null;

  private PreparedStatement preStmt = null;

  public static synchronized DBHandler getHandler(
    String poolName, String handlerID) {
    DBHandler handler = new DBHandler(poolName, handlerID);

    if (firstInstance) { //第一次创建实例
      //需要初始化
      cat.debug("go to init()");
      handler.init();
      //Test
      DBConnectionManager.getInstance();
      firstInstance = false;
    }

    if (configuration == null) {
      cat.debug("config error");
      return null;
    }

    cat.debug("check poolName and handlerID");

    Object object = configuration.get(poolName);

    if (object != null) {
      Querys querys = (Querys)object;
      String sql = querys.getQuery(handlerID);
      if (sql == null) {
        cat.debug("handlerID error");
        handler = null;
      }
      else
        handler.querySQL = sql;
    }
    else {
      cat.debug("can not get pool: " + poolName);
      handler = null;
    }

    if (handler != null) {
      handler.dbConnM = DBConnectionManager.getInstance();

      if (handler.dbConnM != null) {
        handler.conn = handler.dbConnM.getConnection(poolName);

        if (handler.conn != null) {
          cat.debug("got database connection");
        }
        else {
          cat.warn("can not get database connection");
          handler.dbConnM.release();
          handler = null;
        }
      }
      else {
        cat.warn("can not get database manager");
        handler = null;
      }
    }

    return handler;
  }

  public void setInt(int parameterIndex, int x)
      throws SQLException {
    if (this.preStmt == null) {
      this.initPreparedStatement();
    }

    this.preStmt.setInt(parameterIndex, x);
  }

  public void setString(int parameterIndex, String x)
      throws SQLException {
    if (this.preStmt == null) {
      this.initPreparedStatement();
    }

    this.preStmt.setString(parameterIndex, x);
  }

  public int executeUpdate()
      throws SQLException {
    /**
     * @todo executeUpdate(String sql)?
     */
    return this.preStmt.executeUpdate();
  }

  public void close() throws SQLException {
    /**
     * @todo close()?
     */
    if (this.preStmt != null)
      this.preStmt.close();

    if ((this.conn != null) && (this.dbConnM != null)) {
      this.dbConnM.rtnConnection(this.poolName, this.conn);
      this.dbConnM.release();
      this.conn = null;
      this.dbConnM = null;
    }
  }

  private void initPreparedStatement()
      throws SQLException {
    this.preStmt = this.conn.prepareStatement(this.querySQL);
  }

  /**
   * 类内部的自测代码。
   */
  public static void main(String[] args) throws SQLException {
    PropertyConfigurator.configure("log.config");

    for (int i = 0; i < 1024; i++)
    try {
      System.out.println(Runtime.getRuntime().totalMemory());
      DBHandler handler = DBHandler.getHandler("test", "ADD");

      if (handler == null) {
        cat.warn("dbhandler is null");
        return;
      }

      handler.setString(1, "liugang" + i);
      handler.setString(2, "pass");

      handler.executeUpdate();

      handler.close();
    }
    catch (SQLException e) {}
  }

  //私有构造函数
  private DBHandler(String poolName, String handlerID)
  {
    this.poolName = poolName;
    this.handlerID = handlerID;
  }

  private void init() {
    /**
     * @todo 获取配置信息
     */

    //读取配置文件信息
    InputStream is = getClass().getResourceAsStream("/dbhandler.xml");

    //不进行有效性文档检验
    boolean validation = false;

    SAXParserFactory spf = SAXParserFactory.newInstance();
    spf.setValidating(validation);

    XMLReader xmlReader = null;
    try {
      // Create a JAXP SAXParser
      SAXParser saxParser = spf.newSAXParser();

      // Get the encapsulated SAX XMLReader
      xmlReader = saxParser.getXMLReader();
    } catch (Exception ex) {
      cat.error("",ex);
      return;
    }

    // Set the ContentHandler of the XMLReader
    XMLConfigParse configHandler = new XMLConfigParse();
    xmlReader.setContentHandler(configHandler);

    // Set an ErrorHandler before parsing
    xmlReader.setErrorHandler(new XMLConfigParse.MyErrorHandler(System.err));

    try {
      // Tell the XMLReader to parse the XML document
      xmlReader.parse(new InputSource(is));
    } catch (SAXException se) {
      cat.error("",se);
    } catch (IOException ioe) {
      cat.error("",ioe);
    }

    this.configuration = configHandler.getConfiguration();
  }
}

class XMLConfigParse extends DefaultHandler {
    // A Hashtable with tag names as keys and Integers as values
    //private Hashtable tags;

    private Hashtable pools;

    private String nameOfOperation;

    private StringBuffer buffer;

    private Querys querys;

    public Hashtable getConfiguration() {
      return this.pools;
    }

    // Parser calls this once at the beginning of a document
    public void startDocument() throws SAXException {
        //tags = new Hashtable();
        this.pools = new Hashtable();
    }

    // Parser calls this for each element in a document
    public void startElement(String namespaceURI, String localName,
                             String rawName, Attributes atts)
        throws SAXException
    {
      if (localName.equals("DBHandler"))
        return;
      else if (localName.equals("DBPool")) {
        String name = atts.getValue("name");
        String type = atts.getValue("type");

        //System.err.println(name);
        //System.err.println(type);

        if ((name != null) && (type != null)) {
          querys = new Querys();
          querys.setTypeOfDataBase(type);
          pools.put(name, querys);
        }
        else {
          this.querys = null;
        }
      }
      else if (localName.equals("Operation")) {
        if (this.querys != null) {
          this.nameOfOperation = atts.getValue("name");
          this.buffer = new StringBuffer();
        }
      }
    }

    public void characters(char[] ch, int start, int end)
        throws SAXException {
      if (this.buffer != null)
        this.buffer.append(ch, start, end);
    }

    public void endElement(String uri, String localName, String qName)
        throws SAXException {

      if (localName.equals("Operation")) {
        if (this.querys != null) {
          this.querys.addQuery(this.nameOfOperation, buffer.toString().trim());
          //System.err.println(this.nameOfOperation);
          //System.err.println(buffer.toString().trim());

        }
      }
    }

    // Parser calls this once after parsing a document
    public void endDocument() throws SAXException {

    }

    // Error handler to report errors and warnings
    static class MyErrorHandler implements ErrorHandler {
        /** Error handler output goes here */
        private PrintStream out;

        MyErrorHandler(PrintStream out) {
            this.out = out;
        }

        /**
         * Returns a string describing parse exception details
         */
        private String getParseExceptionInfo(SAXParseException spe) {
            String systemId = spe.getSystemId();
            if (systemId == null) {
                systemId = "null";
            }
            String info = "URI=" + systemId +
                " Line=" + spe.getLineNumber() +
                ": " + spe.getMessage();
            return info;
        }

        // The following methods are standard SAX ErrorHandler methods.
        // See SAX documentation for more info.

        public void warning(SAXParseException spe) throws SAXException {
            out.println("Warning: " + getParseExceptionInfo(spe));
        }

        public void error(SAXParseException spe) throws SAXException {
            String message = "Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }

        public void fatalError(SAXParseException spe) throws SAXException {
            String message = "Fatal Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }
    }
}

class Querys {

  private String typeOfDataBase = null;

  private Hashtable querys = null;

  public Querys() {
    this.querys = new Hashtable();
  }

  public void setTypeOfDataBase(String type) {
    this.typeOfDataBase = type;
  }

  public void addQuery(String opID, String sql) {
    /**
     * @todo 将该query加入
     */
    this.querys.put(opID, sql);
  }

  public void delQuery(String opID) {
    /**
     * @todo 将该query删除
     */
  }

  public String getQuery(String opID) {
    /**
     * @todo 获取该query
     */
    return (String)this.querys.get(opID);
  }
}

--
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Email: gang_l@21cn.com & gang_l@hotmail.com
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