map转实体类

Entity entity = JacksonUtils.fromJson(map, Entity.class);

package com.sccl.common.utils;

import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;
import java.util.stream.Collectors;

import org.springframework.util.CollectionUtils;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.sccl.common.collect.OptionalExt;

import lombok.extern.slf4j.Slf4j;

/**
 * @author 
 * @date 2018-07-19
 */
@Slf4j
public class JacksonUtils {

    private static ObjectMapper mapper;
    
    private static ObjectMapper mapperWithNon;

    static {
        mapper = new ObjectMapper();
        //Mon Sep 21 16:25:03 CST 2020
        //Mon Sep 21 16:25:03 CST 2020
        mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY)
                .setTimeZone(TimeZone.getTimeZone("GMT+8"))
                .setDateFormat(new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        //保留空值
        mapperWithNon = new ObjectMapper();
        mapperWithNon.setTimeZone(TimeZone.getTimeZone("GMT+8"))
                .setDateFormat(new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        mapperWithNon.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapperWithNon.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object arg0, JsonGenerator arg1, SerializerProvider arg2) throws IOException, JsonProcessingException {
                arg1.writeString("");
            }
        });
    }

    public static String toJson(Object obj) {
        try {
            return mapper.writeValueAsString(obj);
        } catch (IOException e) {
            if (log.isErrorEnabled()) {
                log.error("Convert bean to json exception. info:{}", e.getMessage());
            }
        }
        return null;
    }
    
    public static String toJsonWithNullValue(Object obj) {
        try {
            return mapperWithNon.writeValueAsString(obj);
        } catch (IOException e) {
            if (log.isErrorEnabled()) {
                log.error("Convert bean to json exception. info:{}", e.getMessage());
            }
        }
        return null;
    }

    public static <T> T fromJson(String json, Class<T> clazz) {
        try {
            return mapper.readValue(json, clazz);
        } catch (IOException e) {
            if (log.isErrorEnabled()) {
                log.error("Convert json to bean through class template failed. info:{}", e.getMessage());
            }
        }
        return null;
    }

    @SuppressWarnings("rawtypes")
    public static <T> T fromJson(Map map, Class<T> clazz) {
        return fromJson(toJson(map), clazz);

    }

    public static <T> T fromJson(String json, TypeReference<T> reference) {
        try {
            return mapper.readValue(json, reference);
        } catch (IOException e) {
            if (log.isErrorEnabled()) {
                log.error("Convert json to bean through TypeReference failed. info:{}", e.getMessage());
            }
        }
        return null;
    }

    /**
     * json 字符串转list<T>
     *
     * @param json
     * @param clazz
     * @return List<T>
     * @Title: toList
     * @author: UFO
     * @date: 2020年9月14日    下午3:43:20
     * @throws:
     */
    public static <T> List<T> toList(String json, Class<T> clazz) {
        TypeFactory typeFactory = mapper.getTypeFactory();
        List<T> list = null;
        try {
            list = mapper.readValue(json, typeFactory.constructCollectionType(List.class, clazz));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

        return list;
    }

    public static <T> List<T> toList(String json, TypeReference<List<T>> reference) {
        List<T> list = null;
        try {
            list = mapper.readValue(json, reference);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

        return list;
    }

    /**
     * 对象转Map
     *
     * @param obj 对象
     * @param <T>
     * @return map
     */
    public static <T> Map<String, Object> toMap(T obj) {
        Map<String, Object> map = new LinkedHashMap<>();
        Class<?> clazz = obj.getClass();

        try {
            for (Field field : clazz.getDeclaredFields()) {
                field.setAccessible(true);
                String fieldName = field.getName();
                map.put(fieldName, OptionalExt.ofNullable(field.get(obj)).orElse(""));
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return map;
    }

    public static <T> List<Map<String, Object>> toMap(List<T> obj) {
        if (CollectionUtils.isEmpty(obj)) {
            return null;
        }
        return obj.stream()
                .map(JacksonUtils::toMap)
                .collect(Collectors.toList());
    }

    /**
     * Map转对象
     *
     * @param map
     * @param clazz 类模板
     * @param <T>
     * @return 对象
     */
    public static <T> T fromMap(Map<String, Object> map, Class<T> clazz) {
        if (map == null) {
            return null;
        }
        T obj = null;
        try {
            obj = clazz.newInstance();
            Field[] fields = clazz.getDeclaredFields();
            for (Field field : fields) {
                int mod = field.getModifiers();
                if (Modifier.isStatic(mod) || Modifier.isFinal(mod)) {
                    continue;
                }
                field.setAccessible(true);
                if (map.containsKey(field.getName())) {
                    field.set(obj, map.get(field.getName()));
                }
            }
        } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }

        return obj;
    }

    public static <T> List<T> fromMap(List<Map<String, Object>> map, Class<T> clazz) {
        if (CollectionUtils.isEmpty(map)) {
            return null;
        }
        return map.stream()
                .map(item -> fromMap(item, clazz))
                .collect(Collectors.toList());
    }


    public static void main(String[] args) {
        /*String str = "{\"name\":\"test_name\",\"code\":\"test_code\",\"age\":20,\"data\":{\"sub\":\"test\",\"name\":\"tom\"}}";
        @SuppressWarnings("unchecked")
        Map<String, Object> obj = fromJson(str, Map.class);
        @SuppressWarnings({"unchecked", "rawtypes"})
        Map<String, Object> data = (Map) obj.get("data");
        System.out.println(data);

        str = "[{\"c1\":\"name\",\"field\":\"name\"},{\"c2\":\"code\",\"field\":\"code\"}]";
        List<Map<String, Object>> list = toList(str, new TypeReference<List<Map<String, Object>>>() {
        });
        System.out.println(list);
        System.out.println(list.get(1).get("field").toString());

        str = "[{\"title\":\"序号\",\"type\":\"index\",\"align\":\"center\",\"width\":50,\"__id\":\"d5dzRn\"},{\"title\":\"类型\",\"key\":\"specName\",\"width\":80,\"__id\":\"qHngF3\"},{\"title\":\"名称\",\"key\":\"name\",\"__id\":\"kUN0Gj\"},{\"title\":\"编码\",\"key\":\"code\",\"__id\":\"6GBfWL\"},{\"title\":\"工程状态\",\"key\":\"projectStatusName\",\"width\":80,\"__id\":\"WWLPPK\"},{\"title\":\"项目管理员\",\"key\":\"managerName\",\"width\":80,\"__id\":\"b1UjWO\"},{\"title\":\"项目管理员联系电话\",\"key\":\"managerTel\",\"width\":120,\"__id\":\"HLSMaD\"},{\"title\":\"施工单位名称\",\"key\":\"constUnitName\",\"__id\":\"8MKkk3\"},{\"title\":\"施工单位联系电话\",\"key\":\"constUnitTel\",\"width\":120,\"__id\":\"flqI3B\"},{\"title\":\"验证状态\",\"key\":\"checkStatusName\",\"width\":80,\"__id\":\"pxA1jv\"},{\"title\":\"操作\",\"key\":\"action\",\"align\":\"center\",\"width\":100,\"__id\":\"1kpUSu\"}]";
        list = toList(str, new TypeReference<List<Map<String, Object>>>() {
        });
        System.out.println(list);*/
    	Map<String, String> map=new HashMap<String, String>();
    	map.put("k1", "v1");
    	map.put("k2", "v2");
    	map.put("k3", "");
    	map.put("k4", null);
    	String str=toJsonWithNullValue(map);
    	System.out.println(str);
    }
}