Question

我的数据库中有三个表格，例如user，authority和role。表权限包含两个字段user_id和role_id，它们是外键。 SQL语句是：

SELECT t1.id id, t3.id user_id, t3.username_x username_x, t2.id role_id, t2.desc_x desc_x
FROM `securitydashboard`.`authorities` AS t1
INNER JOIN `securitydashboard`.`role` AS t2
INNER JOIN `securitydashboard`.`user` AS t3
ON (t2.id = t1.role_id
AND t3.id = t1.user_id);

结果将是：

id user_id username_x role_id desc_x
1  1       admin      1       ROLE_ADMIN
2  1       admin      2       ROLE_USER

我正在设置简单的Spring-Hateoas项目。通过“sql视图”获取上述信息并在Traverson上运行会更容易。我正在努力通过Traverson获取上述信息而没有“sql视图”。我的java程序如下：

public class UserResource extends ResourceSupport {

    public String usernameX;
    public String passwordX;
    public String firstnameX;
    public String lastnameX;
    public EmailAddress emailX;
    public Boolean enabledB;
    public String saltX;
    public AuthoritiesesById authority;

    static class AuthoritiesesById {

        public Roles role;

        static class Roles {
            String descX;
        }
    }
}

public class Test2 {
    private static final     ParameterizedTypeReference<PagedResources<Resource<UserResource>>> TYPE_REFERENCE = new ParameterizedTypeReference<PagedResources<Resource<UserResource>>>() {};

    public static void main(String[] args) throws Exception {
        String urlstring = "http://localhost:8085/RestDashboard";
        URL url = new URL(urlstring);
        URLConnection connection = url.openConnection();
        connection.setRequestProperty("Accept", "application/json");
        LinkDiscoverer discoverer = new HalLinkDiscoverer();
        Link link = discoverer.findLinkWithRel("users", connection.getInputStream());

        URI uri = new URI(urlstring);
        Traverson traverson = new Traverson(uri, MediaTypes.HAL_JSON);
        Map<String, Object> parameters = new HashMap<>();
        PagedResources<Resource<UserResource>> resources = traverson.follow(link.getRel()).withTemplateParameters(parameters).toObject(TYPE_REFERENCE);
        for (Resource<UserResource> resource : resources) {
            System.out.print(resource.getContent().authority.role.descX);
        }
    }
}

结果返回null。

我做错了什么？

Answer 1

我不是100％确定是否是问题，但是您从UserResource延长了ResourceSupport并且您正在使用TypeReference键入Resource，这导致实际上是一样的。请至少尝试使用ResourceSupport或者使用Resource进行扩展，但不要同时使用两个选项。

更新：

尝试使用org.springframework.hateoas.mvc.TypeReferences.PagedResourcesType

实例化您的类型引用

Spring-Hateoas Traverson如何从三个表中获取信息

1 个答案: