Java中的BaseTypeHandler自定义类型转换器的使用

@MappedJdbcTypes(value = JdbcType.VARCHAR)
public class JsonTypeHandler<T extends Object> extends BaseTypeHandler<T> {
    private static ObjectMapper mapper = new ObjectMapper();
    private Class<T> clazz;
    public JsonTypeHandler(Class<T> clazz) {
        if (clazz == null) {
            throw new IllegalArgumentException("Type argument cannot be null");
        }
        this.clazz = clazz;
    }
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws sqlException {
        ps.setString(i, this.toJson(parameter));
    }
    @Override
    public T getNullableResult(ResultSet rs, String columnName) throws SQLException {
        return this.toObject(rs.getString(columnName), clazz);
    }
    @Override
    public T getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return this.toObject(rs.getString(columnIndex), clazz);
    }
    @Override
    public T getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return this.toObject(cs.getString(columnIndex), clazz);
    }
    private String toJson(T object) {
        try {
            return mapper.writeValueAsString(object);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    private T toObject(String content, Class<?> clazz) {
        if (content != null && !content.isEmpty()) {
            try {
                return (T) mapper.readValue(content, clazz);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        } else {
            return null;
        }
    }
}

@MappedJdbcTypes(value = JdbcType.VARCHAR)
@MappedTypes(List.class)
public class JsonListLongTypeHandler extends BaseTypeHandler<List<Long>> {
    private static final ObjectMapper objectMapper = new ObjectMapper();
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, List<Long> parameter, JdbcType jdbcType) throws SQLException {
        ps.setString(i, JSON.toJSONString(parameter));
    }
    @Override
    public List<Long> getNullableResult(ResultSet rs, String columnName) throws SQLException {
        return this.getLongs(rs.getString(columnName));
    }
    @Override
    public List<Long> getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return this.getLongs(rs.getString(columnIndex));
    }
    @Override
    public List<Long> getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return this.getLongs(cs.getString(columnIndex));
    }
    private List<Long> getLongs(String value) {
        if (StringUtils.hasText(value)) {
            try {
                CollectionType type = objectMapper.getTypeFactory().constructCollectionType(ArrayList.class, Long.class);
                Object o1 = objectMapper.readValue(value, type);                List<Long> o = objectMapper.readValue(value, type);
                return o;
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}