泛型实现List＜T＞转List＜U＞

你的名字 2022-09-11 14:26 198阅读 0赞

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# 泛型实现List<T>转List #

*  支持T和U的属性名一致，调用converListT2ListU(List source, Class u)
 *  支持T和U的属性名不一致，调用converListT2ListU(List source, Class u, String relationFields)

用代码说话

/**
 * 将List<T>转为List，T和U赋值的属性名必须一致（底层采用Spring的BeanUtils.copyProperties实现）
 */
 public static <T, U> List converListT2ListU(List<T> source, Class u) {
 return converListT2ListU(source, u, null);
 }
 
 /**
 * 将List<T>转为List，T和U赋值的属性名可以不一致（底层采用Jdk的PropertyDescriptor实现）
 * 如果T和U的属性不一致，可以通过 relationFields 设置
 * 说明：relationFields = "parentId:pid,id,name:userName" 表示T{parentId,id,name}映射为U{pid,id,userName}
 */
 public static <T, U> List converListT2ListU(List<T> source, Class u, String relationFields) {
 if (ObjectUtils.isEmpty(source)) return new ArrayList<>();
 
 if (ObjectUtils.isEmpty(relationFields)) return source.stream().map(e -> {
 try {
 U instanceU = u.newInstance();
 BeanUtils.copyProperties(e, instanceU);
 return instanceU;
 } catch (Exception e1) {
 return null;
 }
 }).collect(Collectors.toList());
 
 Map<String, String> relationMap = convertRelationFields2Map(relationFields);
 List<String> sourceQueryFields = relationMap.keySet().stream().collect(Collectors.toList());
 return source.stream().map(e -> {
 try {
 U instanceU = u.newInstance();
 for (String sourceQueryField : sourceQueryFields) {
 PropertyDescriptor sourcePD = new PropertyDescriptor(sourceQueryField, e.getClass());
 PropertyDescriptor targetPD = new PropertyDescriptor(relationMap.get(sourceQueryField), instanceU.getClass());
 targetPD.getWriteMethod().invoke(instanceU, sourcePD.getReadMethod().invoke(e));
 }
 return instanceU;
 } catch (Exception e1) {
 return null;
 }
 }).collect(Collectors.toList());
 }
 
 /**
 * 将属性关系字符串格式转换为Map格式，如："parentId:pid,id,name:userName"转换为Map={parentId=pid,id=id,name=userName}
 *
 * @param relationFields 属性关系，字符串格式
 * @return 属性关系map格式
 */
 private static Map<String, String> convertRelationFields2Map(String relationFields) {
 Map<String, String> resultMap = new HashMap<>();
 String[] relationFieldArr = relationFields.split(",");
 for (String relationField : relationFieldArr) {
 String[] fieldArr = relationField.split(":");
 resultMap.put(fieldArr[0], fieldArr.length == 1 ? fieldArr[0] : fieldArr[1]);
 }
 return resultMap;
 }