Question

我为我的实体创建了一个自定义反序列化器，但它不断抛出异常：

我有两个类：AppUser和AppUserAvatar

AppUser.java

  <div className="sub-item">{list.email_body.length >= 1 && list.email_body[1]}</div>

AppUserAvatar.java

@Entity
@Table(name = "user")
public class AppUser implements Serializable {

    @Transient
    private static final long serialVersionUID = -3536455219051825651L;

    @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
    @Column(name = "password", nullable = false, length = 256)
    private String password;

    @JsonIgnore
    @Column(name = "is_active", nullable = false)
    private boolean active;

    @JsonIgnore
    @OneToMany(mappedBy = "appUser", targetEntity = AppUserAvatar.class, fetch = FetchType.LAZY)
    private List<AppUserAvatar> appUserAvatars;

    //// Getters and Setters and toString() ////
}

AppUserDeserializer.java 包com.nk.accountservice.deserializer;

@Entity
@Table(name = "user_avatar")
public class AppUserAvatar extends BaseEntityD implements Serializable {

    @Transient
    private static final long serialVersionUID = 8992425872747011681L;

    @Column(name = "avatar", nullable = false)
    @Digits(integer = 20, fraction = 0)
    @NotEmpty
    private Long avatar;

    @JsonDeserialize(using = AppUserDeserializer.class)
    @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false)
    private AppUser appUser;

    //// Getters and Setters and toString() ////
}

样本xhr男孩是：

import com.edoctar.accountservice.config.exception.InputNotFoundException;
import com.edoctar.accountservice.domain.candidate.AppUser;
import com.edoctar.accountservice.service.candidate.AppUserService;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonNode;
import org.springframework.beans.factory.annotation.Autowired;

import java.io.IOException;
import java.io.Serializable;

public class AppUserDeserializer extends JsonDeserializer implements Serializable {

    private static final long serialVersionUID = -9012464195937554378L;

    private AppUserService appUserService;

    @Autowired
    public void setAppUserService(AppUserService appUserService) {
        this.appUserService = appUserService;
    }

    @Override
    public Object deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
        JsonNode node = jsonParser.getCodec().readTree(jsonParser);
        Long userId = node.asLong();
        System.out.println(node);
        System.out.println(node.asLong());
        AppUser appUser = appUserService.findById(userId);
        System.out.println("appuser: " + appUser);
        if (appUser == null) try {
            throw new InputNotFoundException("User not found!");
        } catch (InputNotFoundException e) {
            e.printStackTrace();
            return null;
        }

        return appUser;
    }
}

每次我提交请求时都会引发异常。

{
  "appUser": 1,
  "avatar": 1
}

我发现没有调用appUserService.findById（）方法。我真的很困惑。我不知道哪里出了问题。任何解决方案都将非常有用。谢谢。

Answer 1

更新后的答案： 您不能使用自动装配属性，因为您不在Spring上下文中。您正在通过类AppUserDeserializer作为注释中的引用

@JsonDeserialize(using = AppUserDeserializer.class)

在这种情况下，是 FasterJackson 库创建了AppUserDeserializer的实例，因此没有考虑Autowired注释。

您可以通过一点技巧解决问题。在AppUserService中为spring创建的实例添加静态引用：

 @Service
 public AppUserService {

   public static AppUserService instance;

   public AppUserService() {
     // Modify the constructor setting a static variable holding a
     // reference to the instance created by spring
     AppUserService.instance = this;
   }

   ...
 }

在AppUserDeserializer中使用该引用：

public class AppUserDeserializer extends JsonDeserializer implements Serializable {

    private AppUserService appUserService;

    public AppUserDeserializer() {
      // Set appUserService to the instance created by spring
      this.appUserService = AppUserService.instance;
    }

    ...

}

原始答案：要正确初始化Autowired属性，必须注释类AppUserDeserializer，否则，如果不使用set显式初始化它，则appUserService为null方法。

尝试用AppUserDeserializer注释@Component：

@Component   // Add this annotation
public class AppUserDeserializer extends JsonDeserializer implements Serializable {
   ...
}

Answer 2

尝试更改以下代码行：

private boolean active;

到

private Boolean active;

布尔型原语不能处理null并可能导致NPE。

Answer 3

您可以继续尝试正确注入AppUserService，但根据我的说法，这不是最干净的解决方案。通常，我不喜欢使用@Entity作为通信模型或视图模型的想法。通过这种方式，您可以将实体耦合到视图模型的生产者/消费者。您基本上是在短路模型零件。

我要做的是在反序列化阶段将json的内容映射到另一个类，并在以后使用它构造相应的实体。

杰克逊自定义解串器在春季启动中无法正常工作

3 个答案: