数据库对象映射为java对象,不使用框架

Posted 2020-08-02 Dota_小川

方法:

public static <T> List<T> processResultSetToList(ResultSet rs, Class<T> clazz) throws Exception {
        List<T> ls = new ArrayList<T>();
        Field[] fields = clazz.getDeclaredFields();
        while (rs.next()) {
            T tt = clazz.newInstance();
            for (Field field : fields) {
                try {
                    /**
                     * 如果Oracle数据库中的类型是 number p.getWriteMethod().invoke(tt, new
                     * Object[] { rs.getObject(p.getName()) }) 会报如下错误
                     * java.lang.IllegalArgumentException: argument type
                     * mismatch --- 另外如果mysql数据库中的bigint 在进行setXxxx(Integer
                     * val)时候也会抛出该异常 也会抛出该异常
                     */
                    Object value = null;
                    try {
                        String fieldName = getColumnName(field);
                        switch (TypeUtils.getMappedType(field)) {
                        case Long:
                            value = Long.valueOf(rs.getLong(fieldName));
                            break;
                        case Integer:
                            value = Integer.valueOf(rs.getInt(fieldName));
                            break;
                        case Double:
                            value = Double.valueOf(rs.getDouble(fieldName));
                            break;
                        case Byte:
                            InputStream ins = rs.getBinaryStream(fieldName);
                            if(ins != null){
                                value = IOUtils.toByteArray(ins);
                            }
                            break;
                        case Date:
                            /**
                             * 15-12-8
                             * 转为util.Date
                             */
                            Timestamp t = rs.getTimestamp(fieldName);
                            if(t!=null){
                                value = new Date(t.getTime());
                            }
                            break;
                        default:
                            value = rs.getObject(fieldName);
                            break;
                        }
                    } catch (Exception e) {// 如果仅仅查询Class的部分字段
                        if (e.getMessage().matches("Column\\s+‘.+?‘\\s+not\\s+found.")) {
                            switch (TypeUtils.getMappedType(field)) {
                            case Long:
                            case Integer:
                                value = 0;
                                break;
                            default:
                                value = null;
                                break;
                            }
                        }
                    }
                    field.setAccessible(true);
                    if(value != null){
                        field.set(tt, value);
                    }
                } catch (IllegalArgumentException e) {
                    e.printStackTrace();
                }
            }
            ls.add(tt);
        }
        DBUtils.close(rs, null, null);
        return ls;
    }