Page对象互转Page

原理都是取出Page包装的对象，然后实现对象之间的互传，在返回Page,这里介绍几种实现方式

1. 这个mapper是基于mapStruct，常用来实现Model,DTO的互转，

    <!-- https://mvnrepository.com/artifact/org.mapstruct/mapstruct-jdk8 -->
    <dependency>
        <groupId>org.mapstruct</groupId>
        <artifactId>mapstruct-jdk8</artifactId>
        <version>1.3.0.Final</version>
    </dependency>

引 Jar,pom文件引Jar，还有build插件，Maven 编译等，稍微麻烦些

<plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>1.16.22</version>
                        </path>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>1.3.0.Final</version>
                        </path>
                    </annotationProcessorPaths>
                    <compilerArgs>
                        <arg>-Amapstruct.suppressGeneratorTimestamp=true</arg>
                        <arg>-Amapstruct.defaultComponentModel=spring</arg>
                    </compilerArgs>
                </configuration>
            </plugin>

以下是demo示例

 public Page<CustomerDTO> page2(){
        PageRequest pageRequest = PageRequest.of(0, 20, Sort.Direction.DESC,"customerNumber");
        Page<CustomersEntity> all = customerRepo.findAll(pageRequest);

        Page<CustomerDTO> map = all.map(e -> customerMapper.toCustomerDto(e));
        return map;
    }

2. 基于Json实现对象的互转，这里我用的是Hutool包，（注意这里如果涉及时间类型的字段映射，可能会转换错误）

   public Page<CustomerDTO> page3(){
        PageRequest pageRequest = PageRequest.of(0, 20, Sort.Direction.DESC,"customerNumber");
        Page<CustomersEntity> all = customerRepo.findAll(pageRequest);

        Page<CustomerDTO> map = all.map(e -> JSONUtil.toBean(JSONUtil.toJsonStr(e),CustomerDTO.class));
        return map;
    }

注意，Hutool包的JsonUtil在转换对象的时候，有时候会因为时间类型（LocalDateTime）的字段，转换错误，第一种Mapper方式还没试

3. 使用构造方法实现对象的转换，在V0中定义如下的构造方法即可,注意参数

public MoveRecordVo(MoveInfo moveInfo) {
        this.assetId = moveInfo.getAssetId();
        this.assetName = moveInfo.getAssetName();
        this.startTime = moveInfo.getStartTime();
        this.endTime = moveInfo.getEndTime();
        this.moveTime = null;
        this.moveStatus = moveInfo.getMoveStatus();
        this.remarks = moveInfo.getRemarks();
        this.isOperate = null;
    }

这样在转换对象的时候，就很方便了

Page<MoveInfo> all = moveInfoRepository.findAll(pageRequest);
Page<MoveRecordVo> map = all.map(e -> new MoveRecordVo(e));

4. 还有一种方法，稍微麻烦一点，就是先把Page转成List,再根据之前的分页参数（JPA，根据前端传参，计算好的分页参数Pageable）返回封装Page,代码如下,不想细整理了

public Page<TranscodeRecordVo> findAll(TranscodeDto transcodeDto, int page, int rows, String sord, String sidx) {
        if (StrUtil.isBlankIfStr(sidx)) {
            sidx = "transcodeId";
        }
        PageRequest pageRequest = PageRequest.of(page - 1, rows, Sort.by(Sort.Order.asc(sidx), Sort.Order.desc("collectTime")));
        Page<Transcode> all = transcodeRepository.findAll((Specification<Transcode>) (root, query, cb) -> {
            List<Predicate> predicates = Lists.newArrayList();
            predicates.add(cb.equal(root.get("groupId"), transcodeDto.getGroupId()));

            if (!StrUtil.isBlankIfStr(transcodeDto.getAssetId())) {
                predicates.add(cb.equal(root.get("assetId"), transcodeDto.getAssetId()));
            }
            if (!StrUtil.isBlankIfStr(transcodeDto.getAssetName())) {
                predicates.add(cb.like(root.get("assetName"), "%" + transcodeDto.getAssetName() + "%"));
            }
            if (!StrUtil.isBlankIfStr(transcodeDto.getTranscodeStatus())) {
                predicates.add(cb.equal(root.get("transcodeStatus"), transcodeDto.getTranscodeStatus()));
            }
            if (!StrUtil.isBlankIfStr(transcodeDto.getFromStartTime())) {
                predicates.add(cb.greaterThanOrEqualTo(root.get("endTime"), transcodeDto.getFromStartTime()));
            }
            if (!StrUtil.isBlankIfStr(transcodeDto.getToEndTime())) {
                predicates.add(cb.lessThanOrEqualTo(root.get("endTime"), transcodeDto.getToEndTime()));
            }
            return cb.and(predicates.toArray(new Predicate[0]));
        }, pageRequest);

        ArrayList<TranscodeRecordVo> list = Lists.newArrayList();

        all.getContent().forEach(e -> {
            TranscodeRecordVo vo = new TranscodeRecordVo();
            BeanUtil.copyProperties(e, vo);
            list.add(vo);
        });

        list.forEach(e -> {
            if (NodeResultEnum.TranscodeStatus.STARTED.getKey().equals(e.getTranscodeStatus())) {
                e.setTransTime(DateUtil.formatBetween(ChronoUnit.MILLIS.between(e.getStartTime(), LocalDateTime.now()), BetweenFormater.Level.SECOND));
            } else {
                e.setTransTime(DateUtil.formatBetween(ChronoUnit.MILLIS.between(e.getStartTime(), e.getEndTime()), BetweenFormater.Level.SECOND));
            }
            if (NodeResultEnum.TranscodeStatus.FAILED.getKey().equals(e.getTranscodeStatus())) {
                e.setIsOperate(YesOrNoEnum.YES.getCode());
            } else {
                e.setIsOperate(YesOrNoEnum.NO.getCode());
            }
        });
        return new PageImpl<>(list, all.getPageable(), all.getTotalElements());
    }

这里是我业务中的代码，关于List,Page对象，稍微复杂点的操作

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