Java操作MySQL获取表结构与主外键

 public void getDatabaseMetaData() throws IOException{
        try {           
           DatabaseMetaData dbmd = connection.getMetaData();
              ArrayList<String> tables = new ArrayList<String>();
              ResultSet tableRs = dbmd.getTables(null, null, null, new String[]{"TABLE"});
              System.out.println("--------------graduation数据表-------------");
              while (tableRs.next()) {
              tables.add(tableRs.getString("TABLE_NAME"));
              System.out.println(tableRs.getString("TABLE_NAME")); 
              tablenum++;
            }
            System.out.println("------------------------------------------");                     
            DatabaseMetaData m_DBMetaData = connection.getMetaData();
        ResultSet colRet = m_DBMetaData.getColumns(null,"%", null,"%"); 
        while(colRet.next()) 
        { 
          String columnName = colRet.getString("COLUMN_NAME"); 
          String columnType = colRet.getString("TYPE_NAME"); 
          int datasize = colRet.getInt("COLUMN_SIZE"); 
          int digits = colRet.getInt("DECIMAL_DIGITS"); 
          int nullable = colRet.getInt("NULLABLE"); 
          System.out.println(columnName+" "+columnType+" "+datasize+" "+digits+" "+ 
          nullable+" ");                    
            }                 
        System.out.println("------------------------------------------");
            //获取每张表的主键与外键相关信息         
            for(String table : tables)
            {            
                ResultSet pkRs = dbmd.getPrimaryKeys(null, null, table);
                System.out.print(table + "表的主键有： ");