JMapper将子Collection <entity>转换为Collection <dto>

Question

我尝试将 DemoEntity 转换为 DemoDto 。他们有子属性Collection<SubEntity>和Collection<SubDto>。转换Collection<SubEntity>时发生错误。如果我不添加@JMap("subEntities")，JMapper将运行良好。现在我希望在转换DemoEntity时，Collection<SubEntity>可以一起转换。

public class DemoEntity {

    /** The id. */

    private int id;

    /** The code. */
    private String code;

    /** The date. */
    private Date date;

    private Collection<SubEntity> subEntities;

    @JMapConversion(from = "date", to = "date")
    public String convertDate(Date date) {
        return date.toString();
    }

    public DemoEntity(int id, String code, Date date, Collection<SubEntity> subEntities) {
        super();
        this.id = id;
        this.code = code;
        this.date = date;
        this.subEntities = subEntities;
    }
  

    ...setter and getter...
}

public class DemoDto {

    /** The id. */
    @JMap
    private Long id;

    /** The code. */
    @JMap
    private String code;

    /** The date. */
    @JMap
    private String date;

    @JMap("subEntities")
    private Collection<SubDto> subDtos;

  ... setter and getter...
}

主要方法如下：

        Collection<SubEntity> subEntities = new ArrayList<>();
        for (int i = 1; i < 100; i++) {
            SubEntity subEntity = new SubEntity(i, "C" + i, new Date());
            subEntities.add(subEntity);
        }
        DemoEntity demoEntity = new DemoEntity(1, "D" + 1, new Date(), subEntities);


        JMapperAPI api = new JMapperAPI();
        MappedClass mappedClass = new MappedClass(SubDto.class);
        api.add(mappedClass);
        JMapper<DemoDto, DemoEntity> mapper = new JMapper<>(DemoDto.class, DemoEntity.class, api);
        DemoDto demoDto = mapper.getDestination(demoEntity);
        System.out.println(demoDto);

当隐藏 DemoEntity.subEntities 到 DemoDto.subDtos 时发生异常

Exception in thread "main" com.googlecode.jmapper.exceptions.JMapperException: java.lang.NullPointerException
	at com.googlecode.jmapper.config.JmapperLog.ERROR(JmapperLog.java:46)
	at com.googlecode.jmapper.JMapper.<init>(JMapper.java:445)
	at com.googlecode.jmapper.JMapper.<init>(JMapper.java:411)
	at com.googlecode.jmapper.JMapper.<init>(JMapper.java:385)
	at com.jmapper.JmapperDemo.main(JmapperDemo.java:35)
Caused by: java.lang.NullPointerException
	at com.googlecode.jmapper.operations.complex.AComplexOperation.newInstance(AComplexOperation.java:107)
	at com.googlecode.jmapper.operations.complex.AComplexOperation.newInstance(AComplexOperation.java:98)
	at com.googlecode.jmapper.operations.recursive.MappedCollectionOperation.sharedCode(MappedCollectionOperation.java:64)
	at com.googlecode.jmapper.operations.complex.AComplexOperation.sourceControl(AComplexOperation.java:156)
	at com.googlecode.jmapper.operations.complex.AComplexOperation.genericFlow(AComplexOperation.java:133)
	at com.googlecode.jmapper.operations.complex.AComplexOperation.write(AComplexOperation.java:89)
	at com.googlecode.jmapper.generation.MapperConstructor.mapping(MapperConstructor.java:154)
	at com.googlecode.jmapper.generation.MapperConstructor.wrappedMapping(MapperConstructor.java:123)
	at com.googlecode.jmapper.generation.MapperConstructor.getMappings(MapperConstructor.java:89)
	at com.googlecode.jmapper.generation.MapperGenerator.generateMapperClass(MapperGenerator.java:54)
	at com.googlecode.jmapper.generation.MapperBuilder.generate(MapperBuilder.java:88)
	at com.googlecode.jmapper.JMapper.createMapper(JMapper.java:458)
	at com.googlecode.jmapper.JMapper.<init>(JMapper.java:440)
	... 3 more

此外，是否有任何方法将Collection<Entity>转换为Collection<Dto>

Answer 1

这是递归映射的一种情况，需要映射子类。 当您使用DemoEntity映射DemoDTO时，您需要使用SubEntity映射SubDTO。