MyBatis自定义TypeHandler将Json数组映射为List＜Object＞

原创已于 2024-04-16 14:17:46 修改 · 722 阅读

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CC 4.0 BY-SA版权

文章标签：

#mybatis #json #list

于 2024-04-12 19:38:10 首次发布

文章介绍了如何使用JacksonObjectMapper和BaseTypeHandler在Java中处理SQL查询结果，将包含任意类型的JSON数组转换为List对象，即使数组中元素是嵌套的。

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import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class NestedJsonArrayToObjectListTypeHandler extends BaseTypeHandler<List<Object>> {

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, List<Object> parameter, JdbcType jdbcType) throws SQLException {
        try {
            String json = objectMapper.writeValueAsString(parameter);
            ps.setString(i, json);
        } catch (JsonProcessingException e) {
            throw new SQLException("Error converting list to JSON", e);
        }
    }

    @Override
    public List<Object> getNullableResult(ResultSet rs, String columnName) throws SQLException {
        return jsonStringToList(rs.getString(columnName));
    }

    @Override
    public List<Object> getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return jsonStringToList(rs.getString(columnIndex));
    }

    @Override
    public List<Object> getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return jsonStringToList(cs.getString(columnIndex));
    }

    private List<Object> jsonStringToList(String json) throws SQLException {
        if (json == null || json.isEmpty()) {
            return new ArrayList<>();
        }
        try {
            return parseJsonArray(json);
        } catch (JsonProcessingException e) {
            throw new SQLException("Error converting JSON to list", e);
        }
    }

    private List<Object> parseJsonArray(String jsonArray) throws JsonProcessingException {
        List<Object> result = new ArrayList<>();
        ObjectMapper mapper = new ObjectMapper();
        List<Object> list = mapper.readValue(jsonArray, List.class);
        for (Object obj : list) {
            if (obj instanceof List) {
                result.add(parseJsonArray(mapper.writeValueAsString(obj)));
            } else {
                result.add(obj);
            }
        }
        return result;
    }
}