15p.txt

一本关于JBuilder 应用开发的书籍,希望大家喜欢,其实我没看过的,

class Database
{
//这是一个将 JDBC 数据库的所有功能封装在单个对象中的类
Connection con;
resultSet results;
ResultSetMetaData rsmd;
DatabaseMetaData dma;
String catalog;
String types[];
   public Database(String driver)
   {
    types = new String[1];
    types[0] = "TABLES";         //初始化类型
    try{Class.forName(driver);}  //加载 JDBC-ODBC 桥驱动程序
    catch (Exception e)
    {System.out.println(e.getMessage());}
   }
   //--
   public void Open(String url, String cat)
   {
    catalog = cat;
    try {con = DriverManager.getConnection(url);
    dma =con.getMetaData();   //获取元数据
    }
    catch (Exception e)
    {System.out.println(e.getMessage());}
   }
   //--
   public String[] getTableNames()
   {
    String[] tbnames = null;
    Vector tname = new Vector();
    //将表名添加到一个 Vector 中，
    //因为我们不知道有多少个表
    try {
      results = 
                new resultSet(dma.getTables(catalog, null, 
                        "%", types));
      
      while (results.hasMoreElements())
         tname.addElement(results.getColumnValue("TABLE_NAME"));
      
      }
     catch (Exception e) {System.out.println(e);}
     //将表名复制到一个 String 数组中
      tbnames = new String[tname.size()];
      for (int i=0; i< tname.size(); i++) 
         tbnames[i] = (String)tname.elementAt(i);
      return tbnames;
   }
   //--
   public String[] getTableMetaData()
   {
      // 返回表类型的信息
      results = null;
      try{
      results = 
                new resultSet(dma.getTables(catalog, null, 
                        "%", types));
      }
      catch (Exception e)
      {System.out.println(e.getMessage());}
      return results.getMetaData();
   }
   //--
   public String[] getColumnMetaData(String tablename)
   {
    //返回一个列的数据
    results = null;
    try {
    results = 
                new resultSet(dma.getColumns(catalog, null, 
                        tablename, null));
    }
    catch (Exception e)
   {System.out.println(e.getMessage());}
    return results.getMetaData();
   }
   //--
   public String[] getColumnNames(String table)
   {
   //返回一个列名数组
   String[] tbnames = null;
   Vector tname = new Vector();
   try {
   results = 
                new resultSet(dma.getColumns(catalog, null, 
                        table, null));
    while (results.hasMoreElements() )
       tname.addElement(results.getColumnValue("COLUMN_NAME"));  
      }
   catch (Exception e) {System.out.println(e);}
   tbnames = new String[tname.size()];
   for (int i=0; i< tname.size(); i++) 
      tbnames[i] = (String)tname.elementAt(i);
   return tbnames;
   } 
//--
public String getColumnValue(String table, 
                        String columnName)
   {
   //返回给定列的值 
   String res = null;
   try 
     {
      if (table.length()>0) 
         results =
                         Execute("Select " + columnName +
                                " from " + table + 
                                " order by "+columnName);
      if (results.hasMoreElements())
         res = results.getColumnValue(columnName);
     }
   catch (Exception e)
   {System.out.println("Column value error" +
                columnName+ e.getMessage());}
   return res;
   }
//--
   public String getNextValue(String columnName)
   {
   // 使用存储的 resultSet
   //返回该列的下一个值
      String res = "";
   try 
     {
      if (results.hasMoreElements())
         res = results.getColumnValue(columnName);
     }
   catch (Exception e)
   {System.out.println("next value error"+
                columnName+ e.getMessage());}
   return res;
 }
//--
   public resultSet Execute(String sql)
   {
   //对此数据库执行一个 SQL 查询
   results = null;
   try
      {
      Statement stmt = con.createStatement();
      results = new resultSet(stmt.executeQuery(sql));
    }
    catch (Exception e)
      {System.out.println("execute error"+
                e.getMessage());}
   return results;
   }
}