微服务之间调用外键“翻译”的方法概述

写在前面的话：减少strean流操作，减少多层嵌套for循环。使用普通for循环和map的方式进行转换，

第一步查询数据

List<Student> findList = studentDao.findList(findMap);

第二步准备遍历和赋值

if(CollectionUtil.isNotEmpty(findList)){
            // 第一次遍历，取出所有待翻译的字段，避免重复使用steam流取值
            Set<String> courseSet = new HashSet<>(16);
            Set<String> schooldSet = new HashSet<>(16);
            Set<String> nativePlaceSet = new HashSet<>(16);
            for (Student student : findList) {
                // 课程id
                String courseId = student.getSourceId();
                if(StringUtil.isNotEmpty(courseId)){
                    courseSet.add(courseId);
                }
                // 学校id
                String schooldId = student.getSchoold();
                if(StringUtil.isNotEmpty(schooldId)){
                    schooldSet.add(schooldId);
                }
                // 籍贯id
                String nativePlaceId = student.getNativePlace();
                if(StringUtil.isNotEmpty(nativePlaceId)){
                    nativePlaceSet.add(nativePlaceId);
                }
            }
            // 查询课程信息、学校信息、籍贯信息，并转换成map
            Map<String,Object> findMap = new HashMap<>(16);
            findMap.put("courseSet",courseSet);
            findMap.put("schooldSet",schooldSet);
            findMap.put("nativePlaceSet",nativePlaceSet);
            List<Course> courseList = courseDao.findList(findMap);
            List<Schoold> schooldList = schooldDao.findList(findMap);
            List<NativePlace> nativePlaceList = nativePlaceDao.findList(findMap);
            // 转换成map
            Map<String,Course> courseMap = CollectionUtil.isEmpty(courseList) ? new HashMap<>(0) :
                    courseList.stream().collect(Collectors.toMap(Course::getId, course -> course));
            Map<String,Schoold> schooldMap = CollectionUtil.isEmpty(schooldList) ? new HashMap<>(0) :
                    courseList.stream().collect(Collectors.toMap(Schoold::getId, schoold -> schoold));
            Map<String,NativePlace> nativePlaceMap = CollectionUtil.isEmpty(nativePlaceList) ? new HashMap<>(0) :
                    courseList.stream().collect(Collectors.toMap(NativePlace::getId, nativePlace -> nativePlace));
            // 第二次遍历，填充翻译后的值
            for (Student student : findList) {
                // 课程id-->课程名称
                String courseId = student.getSourceId();
                if(StringUtil.isNotEmpty(courseId)){
                    student.setSourceName(courseMap.get(courseId).getName());
                }
                // 学校id-->学校名称
                String schooldId = student.getSchoold();
                if(StringUtil.isNotEmpty(schooldId)){
                    student.setSchooldName(schooldMap.get(schooldId).getName());
                }
                // 籍贯id-->籍贯名称
                String nativePlaceId = student.getNativePlace();
                if(StringUtil.isNotEmpty(nativePlaceId)){
                    student.setNativePlaceName(nativePlaceMap.get(nativePlaceId).getName());
                }
            }
        }

结语：仅遍历2次，减少了stream流取值。用转map的方式减少了多层for循环。