Java introspection: object to map

Question

I have a Java object obj that has attributes obj.attr1, obj.attr2 etc. The attributes are possibly accessed through an extra level of

Answer 1

maven dependencies

    
        com.fasterxml.jackson.datatype
        jackson-datatype-jsr310
    

....

ObjectMapper m = new ObjectMapper();
Map mappedObject = m.convertValue(myObject,Map.class);

for JSR310 New Date/Time API,there are some issue need to be improved eg:

import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.junit.Test;

import java.sql.Timestamp;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.Map;

@Data
@NoArgsConstructor
public class QueryConditionBuilder
{
    LocalDateTime startTime;
    LocalDateTime endTime;
    Long nodeId;
    Long fsId;
    Long memId;
    Long ifCardId;

    private QueryConditionBuilder(QueryConditionBuilder.Builder builder) {
        setStartTime(builder.startTime);
        setEndTime(builder.endTime);
        setNodeId(builder.nodeId);
        setFsId(builder.fsId);
        setMemId(builder.memId);
        setIfCardId(builder.ifCardId);
    }

    public static QueryConditionBuilder.Builder newBuilder() {
        return new QueryConditionBuilder.Builder();
    }

    public static QueryConditionBuilder newEmptyBuilder() {
        return new QueryConditionBuilder.Builder().build();
    }


    public Map toFilter()
    {
        Map filter = new ObjectMapper().convertValue(this,Map.class);
        System.out.printf("查询条件:%s\n", JSON.toJSONString(filter));
        return filter;
    }

    public static final class Builder {
        private LocalDateTime startTime;
        private LocalDateTime endTime;
        private Long nodeId = null;
        private Long fsId = null;
        private Long memId =null;
        private Long ifCardId = null;

        private Builder() {
        }

        public QueryConditionBuilder.Builder withStartTime(LocalDateTime val) {
            startTime = val;
            return this;
        }

        public QueryConditionBuilder.Builder withEndTime(LocalDateTime val) {
            endTime = val;
            return this;
        }

        public QueryConditionBuilder.Builder withNodeId(Long val) {
            nodeId = val;
            return this;
        }

        public QueryConditionBuilder.Builder withFsId(Long val) {
            fsId = val;
            return this;
        }

        public QueryConditionBuilder.Builder withMemId(Long val) {
            memId = val;
            return this;
        }

        public QueryConditionBuilder.Builder withIfCardId(Long val) {
            ifCardId = val;
            return this;
        }

        public QueryConditionBuilder build() {
            return new QueryConditionBuilder(this);
        }
    }

    @Test
    public void test()
    {     
        LocalDateTime now = LocalDateTime.now(ZoneId.of("+8"));
        LocalDateTime yesterday = now.plusHours(-24);

        Map condition = QueryConditionBuilder.newBuilder()
                .withStartTime(yesterday)
                .withEndTime(now)
                .build().toFilter();

        System.out.println(condition);
    }
}

expects(pseudo-code):

查询条件:{"startTime":{"2019-07-15T20:43:15"},"endTime":{"2019-07-16T20:43:15"}
{startTime={2019-07-15T20:43:15}, endTime={"2019-07-16T20:43:15"}, nodeId=null, fsId=null, memId=null, ifCardId=null}

instead,i got these:

查询条件:{"startTime":{"dayOfMonth":15,"dayOfWeek":"MONDAY","dayOfYear":196,"hour":20,"minute":38,"month":"JULY","monthValue":7,"nano":263000000,"year":2019,"second":12,"chronology":{"id":"ISO","calendarType":"iso8601"}},"endTime":{"dayOfMonth":16,"dayOfWeek":"TUESDAY","dayOfYear":197,"hour":20,"minute":38,"month":"JULY","monthValue":7,"nano":263000000,"year":2019,"second":12,"chronology":{"id":"ISO","calendarType":"iso8601"}}}
{startTime={dayOfMonth=15, dayOfWeek=MONDAY, dayOfYear=196, hour=20, minute=38, month=JULY, monthValue=7, nano=263000000, year=2019, second=12, chronology={id=ISO, calendarType=iso8601}}, endTime={dayOfMonth=16, dayOfWeek=TUESDAY, dayOfYear=197, hour=20, minute=38, month=JULY, monthValue=7, nano=263000000, year=2019, second=12, chronology={id=ISO, calendarType=iso8601}}, nodeId=null, fsId=null, memId=null, ifCardId=null}

after a few research,an effective trick was found,

ObjectMapper mapper = new ObjectMapper();
JavaTimeModule module = new JavaTimeModule();
//https://github.com/networknt/light-4j/issues/82
mapper.registerModule(module);
mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
//incase of empty/null String
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
Map filter = mapper.convertValue(this,Map.class);
System.out.printf("查询条件:%s\n", JSON.toJSONString(filter));
return filter;

output:

查询条件:{"startTime":"2019-07-15T21:29:13.711","endTime":"2019-07-16T21:29:13.711"}
{startTime=2019-07-15T21:29:13.711, endTime=2019-07-16T21:29:13.711, nodeId=null, fsId=null, memId=null, ifCardId=null}

I used the above code for dynamical query in MyBatis
eg.

 /***
     * 查询文件系统使用率
     * @param condition
     * @return
     */
    LinkedList queryFileSystemUsage(Map condition);

    List fooBar()
    { 
       return snmpBaseMapper.queryFileSystemUsage(QueryConditionBuilder
                .newBuilder()
                .withNodeId(nodeId)
                .build()
                .toFilter());
    }