使用sql查询mysql/oracle/sql server/gp数据库中指定表的字段信息(字段名/字段类型/字段长度/是否是主键/是否为空)

1,根据数据库类型拼接不同URL

/**
     * 根据类型不同拼接连接的URL
     * @param dbType 1：mysql、2：oracle、3：sql server、4：gp
     * @param ip
     * @param port
     * @param databaseName
     * @return*/
    public static String getTestDbUrl(int dbType, String ip, String port, String databaseName){
        String url = "";
        if (Constant.DATABASE_TYPE_MYSQL == dbType){
            //mysql
            url = "jdbc:mysql://"+ip+":"+port+"/"+databaseName+"?useUnicode=true&characterEncoding=UTF8";
        }else if (Constant.DATABASE_TYPE_ORACLE == dbType){
            //oracle
            url = "jdbc:oracle:thin:@"+ip+":"+port+":ORCL";
        }else if (Constant.DATABASE_TYPE_SQL_SERVER == dbType){
            //sql server
            url = "jdbc:sqlserver://"+ip+":"+port+";databaseName="+databaseName+";integratedSecurity=true";
        }else if (Constant.DATABASE_TYPE_GP == dbType){
            //gp
            url = "jdbc:postgresql://"+ip+":"+port+"/"+databaseName;
        }
        return url;
    }

2,创建连接并查询

/**
     * 通过jsbc获取数据
     * @param driver driver
     * @param url 数据库url
     * @param username 用户名
     * @param password 密码
     * @param sql sql语句
     * @param sqlType 语句类型 ，1：查询语句，2：创建语句
     * @param columnConnt 查询语句返回列的个数
     * @return List
     */
    public static List<Map<String, String>> getJdbcData(String driver, String url, String username, String password, String sql, int sqlType, int columnConnt){
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        List<Map<String, String>> result = new ArrayList<>();
        try {
            //1.加载oracle数据库驱动
            Class.forName(driver);
            //2.获取数据库连接
            con = DriverManager.getConnection(url, username, password);
            //3.获取执行sql语句的平台
            st = con.createStatement();
            //4.执行sql语句获取结果集
            // 查询
            if(sqlType == 1){
                rs = st.executeQuery(sql);
                //5.循环获取结果集数据
                int i = 1;
                while(rs.next()){
                    if(i <= columnConnt){
                        Map<String, String> resultMap = new HashMap<>(columnConnt);
                        for (int j = 0; j < columnConnt; j++) {
                            resultMap.put("column" + (j + 1) + "", rs.getString(j + 1));
                        }
                        result.add(resultMap);
                    }
                }
            }else{
                // 创建
                int rss = st.executeUpdate(sql);
                Map<String, String> resultMap = new HashMap<>(columnConnt);
                resultMap.put("column" + 1 + "", rss + "");
                result.add(resultMap);
            }
            return result;
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            Map<String, String> resultMap = new HashMap<>(columnConnt);
            resultMap.put("column1", "-1");
            result.add(resultMap);
        } catch (SQLException e) {
            e.printStackTrace();
            Map<String, String> resultMap = new HashMap<>(columnConnt);
            resultMap.put("column1", "-1");
            result.add(resultMap);
        }finally{
            //关闭rs
            if(rs != null){
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            //关闭st
            if(st != null){
                try {
                    st.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            //关闭con
            if(con != null){
                try {
                    con.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            return result;
        }
//        return result;
    }

3,设置参数

/**
     * 查询指定数据库中指定表的字段信息
     * @param databaseType 数据库类型: 1：mysql、2：oracle、3：sql server、4：gp
     * @param databaseName 数据库名称
     * @param databaseIp 数据库ip
     * @param databasePort 数据库端口
     * @param databaseUserName 数据库用户名
     * @param databaseUserPassword 数据库用户的密码
     * @param tableName 表名
     * @return*/
    public static List<Map<String, String>> getColumnInfoByTableName(int databaseType, String databaseName, String databaseIp, String databasePort, String databaseUserName,
                                                String databaseUserPassword, String tableName){
        String sql = "";
        if (Constant.DATABASE_TYPE_MYSQL == databaseType){
            //mysql
            sql = "SELECT column_name, data_type,(case when data_type = 'int' or  data_type = 'float' or data_type = 'double' or data_type = 'decimal' then NUMERIC_PRECISION else CHARACTER_MAXIMUM_LENGTH end ) as data_length,
" +
                    "(case when IS_NULLABLE = 'NO' then 0 else 1 end)as data_Null,(case when COLUMN_KEY='PRI' then 1 else 0 end) as data_IsPK
" +
                    " FROM information_schema.COLUMNS WHERE table_schema = '"+databaseName+"' and table_name = '"+tableName+"'";
        }else if (Constant.DATABASE_TYPE_ORACLE == databaseType){
            //oracle
            sql = "SELECT column_name, data_type, data_length, NULLABLE,(case when column_name=(select col.column_name 
" +
                    "from user_constraints con,  user_cons_columns col 
" +
                    "where con.constraint_name = col.constraint_name 
" +
                    "and con.constraint_type='P' 
" +
                    "and col.table_name = "+tableName+"
" +
                    ") then 1 else 0 end) as IsPK
" +
                    "  FROM all_tab_cols
" +
                    " WHERE table_name = '"+tableName+"' ";
        }else if (Constant.DATABASE_TYPE_SQL_SERVER == databaseType){
            //sql server
            sql = "SELECT C.name as column_name, T.name as data_type, COLUMNPROPERTY(C.id,C.name,'PRECISION') as data_length, 
" +
                    "convert(bit,case when exists(SELECT 1 FROM sysobjects where xtype='PK' and parent_obj=c.id and name in (
" +
                    "         SELECT name FROM sysindexes WHERE indid in(
" +
                    "             SELECT indid FROM sysindexkeys WHERE id = c.id AND colid=c.colid))) then 1 else 0 end) 
" +
                    "                 as data_IsPK, convert(bit,C.IsNullable) as data_Null
" +
                    "FROM syscolumns C INNER JOIN systypes T ON C.xusertype = T.xusertype 
" +
                    "inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties' 
" +
                    "where T.name is not null
" +
                    "and d.name='"+tableName+"'";
        }else if (Constant.DATABASE_TYPE_GP == databaseType){
            //gp

        }
        List<Map<String, String>> columnNameList = JdbcUtil.getJdbcData(SingletonHoldResource.getInstance().getDictMap(Constant.DB_DRIVER).get(Integer.toString(databaseType)),
                getTestDbUrl(databaseType, databaseIp, databasePort, databaseName),
                databaseUserName, databaseUserPassword,
                sql,
                1, 5);
        //结果中的对应关系:column1 -- name; column2 -- type; column3 -- length; column4 -- IsNull; column5 -- isPk;
        return columnNameList;
    }