如何使用Spring Data REST创建自定义PersistentEntityResourceAssembler

Question

我使用的是Spring Boot 2.1，Spring Data REST，Spring HATEOAS，Hibernate 5。

我正在寻找一种在REST调用中过滤字段的方法。我将使用https://github.com/bohnman/squiggly-java，但我希望将其集成到Spring资源汇编程序中。

我正在寻找一种方法来定制在REST控制器中自动可用的PersistentEntityResourceAssembler。这是类的代码：

public class PersistentEntityResourceAssembler implements ResourceAssembler<Object, PersistentEntityResource> {
    @NonNull
    private final PersistentEntities entities;
    @NonNull
    private final Projector projector;
    @NonNull
    private final Associations associations;
    @NonNull
    private final SelfLinkProvider linkProvider;
    @NonNull
    private final EmbeddedWrappers wrappers = new EmbeddedWrappers(false);

    public PersistentEntityResource toResource(Object instance) {
        Assert.notNull(instance, "Entity instance must not be null!");
        return this.wrap(this.projector.projectExcerpt(instance), instance).build();
    }

    public PersistentEntityResource toFullResource(Object instance) {
        Assert.notNull(instance, "Entity instance must not be null!");
        return this.wrap(this.projector.project(instance), instance).build();
    }

    private Builder wrap(Object instance, Object source) {
        PersistentEntity<?, ?> entity = this.entities.getRequiredPersistentEntity(source.getClass());
        return PersistentEntityResource.build(instance, entity).withEmbedded(this.getEmbeddedResources(source)).withLink(this.getSelfLinkFor(source)).withLink(this.linkProvider.createSelfLinkFor(source));
    }

    private Iterable<EmbeddedWrapper> getEmbeddedResources(Object instance) {
        return (new EmbeddedResourcesAssembler(this.entities, this.associations, this.projector)).getEmbeddedResources(instance);
    }

    public Link getSelfLinkFor(Object instance) {
        Link link = this.linkProvider.createSelfLinkFor(instance);
        return new Link(link.expand(new Object[0]).getHref(), "self");
    }

    public PersistentEntityResourceAssembler(@NonNull PersistentEntities entities, @NonNull Projector projector, @NonNull Associations associations, @NonNull SelfLinkProvider linkProvider) {
        if (entities == null) {
            throw new IllegalArgumentException("entities is marked @NonNull but is null");
        } else if (projector == null) {
            throw new IllegalArgumentException("projector is marked @NonNull but is null");
        } else if (associations == null) {
            throw new IllegalArgumentException("associations is marked @NonNull but is null");
        } else if (linkProvider == null) {
            throw new IllegalArgumentException("linkProvider is marked @NonNull but is null");
        } else {
            this.entities = entities;
            this.projector = projector;
            this.associations = associations;
            this.linkProvider = linkProvider;
        }
    }
}

我的猜测是它被注入到Spring中的某个地方。我想动态定制JSON内容，过滤掉我不想要的字段。我试图创建一个类的副本，并用@Component对其进行注释，但它缺少Projector。

在Spring Data REST中定制PersistentEntityResourceAssembler的正确方法是什么？

Answer 1

您必须创建一个PersistentEntityResourceAssemblerArgumentResolver，以便在控制器方法需要时动态创建PersistentEntityResourceAssembler。

它是这样工作的，因为PersistentEntityResourceAssembler需要请求中的projection参数，所以它不能是bean__。

参数解析器本身在RepositoryRestMvcConfiguration类中注册。它在其受保护的方法中定义：defaultMethodArgumentResolvers()。不幸的是，它不能通过RepositoryRestConfigurer进行配置，因此您需要扩展RepositoryRestMvcConfiguration配置类本身，然后覆盖defaultMethodArgumentResolvers()方法。

不幸的是，此方法还创建了许多其他argumentResolvers，因此我认为最好的方法是调用超级方法，从返回列表中删除原始PersistentEntityResourceAssemblerArgumentResolver，然后将您的自定义one添加到其中。

这不会是一件容易的事。祝好运!