查询数据转换为树结构
文章目录
-
- 方法一：通用法
- 方法二： java8 Stream()
方法一：通用法
将查询列表循环遍历，有子级的挂上子级，没有子级的单独成顶级
public static List<TSysMenu> toMenuTreeList(List oldList) throws Exception {
String prePid = "-1";
List<Map<String,Object>> tmpList = new ArrayList<>();
Map<String, List<Map<String,Object>>> childMap = new HashMap<>();
Map<String, Map<String,Object>> allMap = new HashMap<>();
for (Object obj : oldList) {
Map<String,Object> menuJSON = MapperUtils.json2mapDeeply(MapperUtils.obj2json(obj));
if (!menuJSON.get("pid").equals(prePid ) && !"-1".equals(prePid)) {
if (allMap.containsKey(prePid) && !allMap.get(prePid).containsKey("children")) {
allMap.get(prePid).put("children", tmpList);
} else {
childMap.put(prePid, tmpList);
}
tmpList = new ArrayList<>();
}
if (childMap.containsKey(menuJSON.get("id"))) {
//菜单有子菜单，安装上
menuJSON.put("children", childMap.get(menuJSON.get("id")));
childMap.remove(menuJSON.get("id"));
}
prePid = (String) menuJSON.get("pid");
tmpList.add(menuJSON);
allMap.put((String) menuJSON.get("id"), menuJSON);
}
if(childMap.size() > 0){
for(List<Map<String,Object>> child : childMap.values()){
tmpList.addAll(child);
}
}
List<TSysMenu> tSysMenus = MapperUtils.json2list(MapperUtils.obj2json(tmpList), TSysMenu.class);
return tSysMenus;
}
MapperUtils 类：
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MapperUtils {
private final static ObjectMapper objectMapper = new ObjectMapper();
static {
JavaTimeModule javaTimeModule = new JavaTimeModule();
javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
javaTimeModule.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
javaTimeModule.addDeserializer(LocalTime.class, new LocalTimeDeserializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
objectMapper.registerModule(javaTimeModule);
}
/**
* 转换为 JSON 字符串
*
* @param obj
* @return
* @throws Exception
*/
public static String obj2json(Object obj) throws Exception {
objectMapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);
return objectMapper.writeValueAsString(obj);
}
/**
* 转换为 JSON 字符串，忽略空值
*
* @param obj
* @return
* @throws Exception
*/
public static String obj2jsonIgnoreNull(Object obj) throws Exception {
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
return objectMapper.writeValueAsString(obj);
}
/**
* 转换为 JavaBean
*
* @param jsonString
* @param clazz
* @return
* @throws Exception
*/
public static <T> T json2pojo(String jsonString, Class<T> clazz) throws Exception {
objectMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
return objectMapper.readValue(jsonString, clazz);
}
/**
* 字符串转换为 Map
*
* @param jsonString
* @return
* @throws Exception
*/
public static <T> Map<String, Object> json2map(String jsonString) throws Exception {
ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
return mapper.readValue(jsonString, Map.class);
}
/**
* 字符串转换为 Map
*/
public static <T> Map<String, T> json2map(String jsonString, Class<T> clazz) throws Exception {
Map<String, Map<String, Object>> map = (Map<String, Map<String, Object>>) objectMapper.readValue(jsonString, new TypeReference<Map<String, T>>() {
});
Map<String, T> result = new HashMap<String, T>();
for (Map.Entry<String, Map<String, Object>> entry : map.entrySet()) {
result.put(entry.getKey(), map2pojo(entry.getValue(), clazz));
}
return result;
}
/**
* 深度转换 JSON 成 Map
*
* @param json
* @return
*/
public static Map<String, Object> json2mapDeeply(String json) throws Exception {
return json2MapRecursion(json, objectMapper);
}
/**
* 把 JSON 解析成 List，如果 List 内部的元素存在 jsonString，继续解析
*
* @param json
* @param mapper 解析工具
* @return
* @throws Exception
*/
private static List<Object> json2ListRecursion(String json, ObjectMapper mapper) throws Exception {
if (json == null) {
return null;
}
List<Object> list = mapper.readValue(json, List.class);
for (Object obj : list) {
if (obj != null && obj instanceof String) {
String str = (String) obj;
if (str.startsWith("[")) {
obj = json2ListRecursion(str, mapper);
} else if (obj.toString().startsWith("{")) {
obj = json2MapRecursion(str, mapper);
}
}
}
return list;
}
/**
* 把 JSON 解析成 Map，如果 Map 内部的 Value 存在 jsonString，继续解析
*
* @param json
* @param mapper
* @return
* @throws Exception
*/
private static Map<String, Object> json2MapRecursion(String json, ObjectMapper mapper) throws Exception {
if (json == null) {
return null;
}
Map<String, Object> map = mapper.readValue(json, Map.class);
for (Map.Entry<String, Object> entry : map.entrySet()) {
Object obj = entry.getValue();
if (obj != null && obj instanceof String) {
String str = ((String) obj);
if (str.startsWith("[")) {
List<?> list = json2ListRecursion(str, mapper);
map.put(entry.getKey(), list);
} else if (str.startsWith("{")) {
Map<String, Object> mapRecursion = json2MapRecursion(str, mapper);
map.put(entry.getKey(), mapRecursion);
}
}
}
return map;
}
/**
* 将 JSON 数组转换为集合
*
* @param jsonArrayStr
* @param clazz
* @return
* @throws Exception
*/
public static <T> List<T> json2list(String jsonArrayStr, Class<T> clazz) throws Exception {
JavaType javaType = getCollectionType(ArrayList.class, clazz);
List<T> list = objectMapper.readValue(jsonArrayStr, javaType);
return list;
}
/**
* 获取泛型的 Collection Type
*
* @param collectionClass 泛型的Collection
* @param elementClasses 元素类
* @return JavaType Java类型
* @since 1.0
*/
public static JavaType getCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {
return objectMapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);
}
/**
* 将 Map 转换为 JavaBean
*
* @param map
* @param clazz
* @return
*/
public static <T> T map2pojo(Map map, Class<T> clazz) {
return objectMapper.convertValue(map, clazz);
}
/**
* 将 Map 转换为 JSON
*
* @param map
* @return
*/
public static String mapToJson(Map map) {
try {
return objectMapper.writeValueAsString(map);
} catch (Exception e) {
e.printStackTrace();
}
return "";
}
/**
* 将 JSON 对象转换为 JavaBean
*
* @param obj
* @param clazz
* @return
*/
public static <T> T obj2pojo(Object obj, Class<T> clazz) {
return objectMapper.convertValue(obj, clazz);
}
}
方法二： java8 Stream()
- 首先筛选父id =0 的集合，并设置他们的子集
- 创建 设置子菜单递归方法，筛选父级id = 当前菜单id 的集合，再执行设置子菜单递归方法。
@Override
public List<SysMenuVO> buildMenuTree(List<SysMenuVO> menuVOList) {
// 判断 menuVOList 里面parentId 是否包含 0 ，如果不包含则反向查询父菜单并添加到 menuVOList
Set<Long> menuIds = menuVOList.stream().map(SysMenuVO::getMenuId).collect(Collectors.toSet());
Set<Long> parentIds = menuVOList.stream().map(SysMenuVO::getParentId).collect(Collectors.toSet());
if(!parentIds.contains(new Long(0))){
if (!CollectionUtils.isEmpty(menuVOList)){
Set<SysMenuVO> parentCollectSet = new HashSet<>();
for (SysMenuVO sysMenuVO : menuVOList){
SysMenuVO parentMenuVO = this.sysMenuMapper.getSysMenuVOByMenuId(sysMenuVO.getParentId());
if (parentMenuVO !=null &&!menuIds.contains(parentMenuVO.getMenuId())){
parentCollectSet.add(parentMenuVO);
}
}
menuVOList.addAll(parentCollectSet);
}
}
List<SysMenuVO> sysMenuVOList = menuVOList.stream()
.filter(item -> item.getParentId().longValue() == 0L)
.map(menuVO -> {
menuVO.setChildren(setMenuChildren(menuVO, menuVOList));
return menuVO;
})
.collect(Collectors.toList());
return sysMenuVOList;
}
private List<SysMenuVO> setMenuChildren(SysMenuVO menuVO, List<SysMenuVO> menuVOList) {
List<SysMenuVO> list = menuVOList.stream()
.filter(f -> f.getParentId().longValue() == menuVO.getMenuId().longValue())
.map(item -> {
item.setChildren(setMenuChildren(item, menuVOList));
return item;
})
.collect(Collectors.toList());
return list;
}