@Test 
public void createXls() throws Exception{
  //声明一个工作薄
  HSSFWorkbook wb = new HSSFWorkbook();
  //声明表
  HSSFSheet sheet = wb.createSheet("第一个表");
  //声明行
  HSSFRow row = sheet.createRow(7);
  //声明列
  HSSFCell cel = row.createCell(3);
  //写入数据
  cel.setCellValue("你也好");
  
  FileOutputStream fileOut = new FileOutputStream("d:/a/b.xls");
  wb.write(fileOut);
  fileOut.close();
 }

@Test
 public void export() throws Exception{
  //声明需要导出的数据库
  String dbName = "focus";
  //声明book
  HSSFWorkbook book = new HSSFWorkbook();
  //获取Connection,获取db的元数据
  Connection con = DataSourceUtils.getConn();
  //声明statemen
  Statement st = con.createStatement();
  //st.execute("use "+dbName);
  DatabaseMetaData dmd = con.getMetaData();
  //获取数据库有多少表
  ResultSet rs = dmd.getTables(dbName,dbName,null,new String[]{"TABLE"});
  //获取所有表名　－　就是一个sheet
  List<String> tables = new ArrayList<String>();
  while(rs.next()){
   String tableName = rs.getString("TABLE_NAME");
   tables.add(tableName);
  }
  for(String tableName:tables){
   HSSFSheet sheet = book.createSheet(tableName);
   //声明sql
   String sql = "select * from "+dbName+"."+tableName;
   //查询数据
   rs = st.executeQuery(sql);
   //根据查询的结果，分析结果集的元数据
   ResultSetMetaData rsmd = rs.getMetaData();
   //获取这个查询有多少行
   int cols = rsmd.getColumnCount();
   //获取所有列名
   //创建第一行
   HSSFRow row = sheet.createRow(0);
   for(int i=0;i<cols;i++){
    String colName = rsmd.getColumnName(i+1);
    //创建一个新的列
    HSSFCell cell = row.createCell(i);
    //写入列名
    cell.setCellValue(colName);
   }
   //遍历数据
   int index = 1;
   while(rs.next()){
    row = sheet.createRow(index++);
    //声明列
    for(int i=0;i<cols;i++){
     String val = rs.getString(i+1);
     //声明列
     HSSFCell cel = row.createCell(i);
     //放数据
     cel.setCellValue(val);
    }
   }
  }
  con.close();
  book.write(new FileOutputStream("d:/a/"+dbName+".xls"));
 }