0

以下情景。

具有以下类的小型 SpringBoot 应用程序：

美食：

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import java.util.LinkedList;
import java.util.List;
import org.immutables.value.Value;

@Value.Immutable
@JsonDeserialize(builder = FooDto.Builder.class)
public interface FooDto{
  @JsonProperty("fee")
  String getFee();

  @JsonProperty("fii")
  String getFii();

  @JsonProperty("url")
  String getUrl();

  @Value.Default
  @JsonProperty("values")
  default String[] getValues(){
    return new String[0];
  }
}

FooJsonMapper：

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;

import org.springframework.stereotype.Component;

@Component
/*package*/ class FooJsonMapper {
  private final ObjectMapper objectMapper;

  FooJsonMapper() {
    objectMapper = new ObjectMapper();
    objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
    objectMapper.disable(DeserializationFeature.FAIL_ON_IGNORED_PROPERTIES);
  }

  public List<FooDto> toDtos(File jsonFile) throws IOException {
    return Arrays.asList(objectMapper.readValue(jsonFile, FooDto[].class));
  }
}

和这样的 JSON：

[
  {
    "fee":"SOME_MESSAGE",
    "fii":"SOME_TECH_MESSAGE",
    "url":"/some",
    "values":[
      "test",
      "some"
    ]
  },
  {
    "fee":"OTHER_MESSAGE",
    "fii":"OTHER_TECH_MESSAGE",
    "url":"/other",
    "values":[
      "other",
      "some"
    ]
  },
  {
    "fee":"4711_MESSAGE",
    "fii":"4711_TECH_MESSAGE",
    "url":"/4711",
    "values":[
      
    ]
  }
]

不知何故，当运行代码杰克逊报告如下：

com.fasterxml.jackson.databind.exc.ValueInstantiationException: Cannot construct instance of `org.some.package.ImmutableFooDto$Builder`, problem: Cannot build FooDto, some of required attributes are not set [fee, fii, url]
 at [Source: (File); line: 13, column: 3] (through reference chain: java.lang.Object[][0])
    at com.fasterxml.jackson.databind.exc.ValueInstantiationException.from(ValueInstantiationException.java:47) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1907) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.handleInstantiationProblem(DeserializationContext.java:1260) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.wrapInstantiationProblem(BeanDeserializerBase.java:1865) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BuilderBasedDeserializer.finishBuild(BuilderBasedDeserializer.java:202) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BuilderBasedDeserializer.deserialize(BuilderBasedDeserializer.java:217) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:214) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:24) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3413) ~[jackson-databind-2.12.3.jar:2.12.3]
    at org.some.package.FooJsonMapper.toDtos(FooJsonMapper.java:25) ~[classes/:na]

我可以确认 json 是正确的，因为以下代码行Object使用其中的数据创建 s：

return Arrays.asList(objectMapper.readValue(jsonFile, Object[].class));

我也尝试@Value.Style(builder = "new")在FooDto.class这里使用：https ://immutables.github.io/json.html

  • 杰克逊：2.12.3
  • org.immutables：2.8.2

编辑：

根据要求使用 Builder 的 ImmutableDTO：

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import javax.annotation.Generated;

/**
 * Immutable implementation of {@link FooDto}.
 * <p>
 * Use the builder to create immutable instances:
 * {@code ImmutableFooDto.builder()}.
 */
@SuppressWarnings("all")
@Generated({"Immutables.generator", "FooDto"})
public final class ImmutableFooDto implements FooDto {
  private final String fee;
  private final String fii;
  private final String url;
  private final String[] values;

  private ImmutableFooDto(ImmutableFooDto.Builder builder) {
    this.fee = builder.fee;
    this.fii = builder.fii;
    this.url = builder.url;
    if (builder.values != null) {
      initShim.values(builder.values);
    }
    this.values = initShim.getValues();
    this.initShim = null;
  }

  private ImmutableFooDto(
      String fee,
      String fii,
      String url,
      String[] values) {
    this.fee = fee;
    this.fii = fii;
    this.url = url;
    this.values = values;
    this.initShim = null;
  }

  private static final int STAGE_INITIALIZING = -1;
  private static final int STAGE_UNINITIALIZED = 0;
  private static final int STAGE_INITIALIZED = 1;
  private transient volatile InitShim initShim = new InitShim();

  private final class InitShim {
    private String[] values;
    private int valuesStage;

    String[] getValues() {
      if (valuesStage == STAGE_INITIALIZING) throw new IllegalStateException(formatInitCycleMessage());
      if (valuesStage == STAGE_UNINITIALIZED) {
        valuesStage = STAGE_INITIALIZING;
        this.values = getValuesInitialize().clone();
        valuesStage = STAGE_INITIALIZED;
      }
      return this.values;
    }

    void values(String[] values) {
      this.values = values;
      valuesStage = STAGE_INITIALIZED;
    }

    private String formatInitCycleMessage() {
      ArrayList<String> attributes = new ArrayList<String>();
      if (valuesStage == STAGE_INITIALIZING) attributes.add("values");
      return "Cannot build FooDto, attribute initializers form cycle" + attributes;
    }
  }

  private String[] getValuesInitialize() {
    return FooDto.super.getValues();
  }

  /**
   * @return The value of the {@code fee} attribute
   */
  @JsonProperty("fee")
  @Override
  public String getFee() {
    return fee;
  }

  /**
   * @return The value of the {@code fii} attribute
   */
  @JsonProperty("fii")
  @Override
  public String getFii() {
    return fii;
  }

  /**
   * @return The value of the {@code url} attribute
   */
  @JsonProperty("url")
  @Override
  public String getUrl() {
    return url;
  }

  /**
   * @return A cloned {@code values} array
   */
  @JsonProperty("values")
  @Override
  public String[] getValues() {
    InitShim shim = this.initShim;
    return shim != null
      ? shim.getValues().clone()
      : this.values.clone();
  }

  /**
   * Copy the current immutable object by setting a value for the {@link FooDto#getFee() fee} attribute.
   * An equals check used to prevent copying of the same value by returning {@code this}.
   * @param fee A new value for fee
   * @return A modified copy of the {@code this} object
   */
  public final ImmutableFooDto withFee(String fee) {
    if (this.fee.equals(fee)) return this;
    String newValue = Objects.requireNonNull(fee, "fee");
    return new ImmutableFooDto(newValue, this.fii, this.url, this.values);
  }

  /**
   * Copy the current immutable object by setting a value for the {@link FooDto#getFii() fii} attribute.
   * An equals check used to prevent copying of the same value by returning {@code this}.
   * @param fii A new value for fii
   * @return A modified copy of the {@code this} object
   */
  public final ImmutableFooDto withFii(String fii) {
    if (this.fii.equals(fii)) return this;
    String newValue = Objects.requireNonNull(fii, "fii");
    return new ImmutableFooDto(this.fee, newValue, this.url, this.values);
  }

  /**
   * Copy the current immutable object by setting a value for the {@link FooDto#getUrl() url} attribute.
   * An equals check used to prevent copying of the same value by returning {@code this}.
   * @param url A new value for url
   * @return A modified copy of the {@code this} object
   */
  public final ImmutableFooDto withUrl(String url) {
    if (this.url.equals(url)) return this;
    String newValue = Objects.requireNonNull(url, "url");
    return new ImmutableFooDto(this.fee, this.fii, newValue, this.values);
  }

  /**
   * Copy the current immutable object with elements that replace the content of {@link FooDto#getValues() values}.
   * The array is cloned before being saved as attribute values.
   * @param elements The non-null elements for values
   * @return A modified copy of {@code this} object
   */
  public final ImmutableFooDto withValues(String... elements) {
    String[] newValue = elements.clone();
    return new ImmutableFooDto(this.fee, this.fii, this.url, newValue);
  }

  /**
   * This instance is equal to all instances of {@code ImmutableFooDto} that have equal attribute values.
   * @return {@code true} if {@code this} is equal to {@code another} instance
   */
  @Override
  public boolean equals(Object another) {
    if (this == another) return true;
    return another instanceof ImmutableFooDto
        && equalTo((ImmutableFooDto) another);
  }

  private boolean equalTo(ImmutableFooDto another) {
    return fee.equals(another.fee)
        && fii.equals(another.fii)
        && url.equals(another.url)
        && Arrays.equals(values, another.values);
  }

  /**
   * Computes a hash code from attributes: {@code fee}, {@code fii}, {@code url}, {@code values}, {@code roles}.
   * @return hashCode value
   */
  @Override
  public int hashCode() {
    int h = 31;
    h = h * 17 + fee.hashCode();
    h = h * 17 + fii.hashCode();
    h = h * 17 + url.hashCode();
    h = h * 17 + Arrays.hashCode(values);
    return h;
  }

  /**
   * Prints the immutable value {@code FooDto} with attribute values.
   * @return A string representation of the value
   */
  @Override
  public String toString() {
    return "FooDto{"
        + "fee=" + fee
        + ", fii=" + fii
        + ", url=" + url
        + ", values=" + Arrays.toString(values)
        + "}";
  }

  /**
   * Utility type used to correctly read immutable object from JSON representation.
   * @deprecated Do not use this type directly, it exists only for the <em>Jackson</em>-binding infrastructure
   */
  @Deprecated
  @JsonDeserialize
  @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.NONE)
  static final class Json implements FooDto {
    String fee;
    String fii;
    String url;
    String[] values;
    List<String> roles = Collections.emptyList();
    boolean rolesIsSet;
    @JsonProperty("fee")
    public void setFee(String fee) {
      this.fee = fee;
    }
    @JsonProperty("fii")
    public void setFii(String fii) {
      this.fii = fii;
    }
    @JsonProperty("url")
    public void setUrl(String url) {
      this.url = url;
    }
    @JsonProperty("values")
    public void setValues(String[] values) {
      this.values = values;
    }
    @Override
    public String getFee() { throw new UnsupportedOperationException(); }
    @Override
    public String getFii() { throw new UnsupportedOperationException(); }
    @Override
    public String getUrl() { throw new UnsupportedOperationException(); }
    @Override
    public String[] getValues() { throw new UnsupportedOperationException(); }
  }

  /**
   * @param json A JSON-bindable data structure
   * @return An immutable value type
   * @deprecated Do not use this method directly, it exists only for the <em>Jackson</em>-binding infrastructure
   */
  @Deprecated
  @JsonCreator
  static ImmutableFooDto fromJson(Json json) {
    ImmutableFooDto.Builder builder = ImmutableFooDto.builder();
    if (json.fee != null) {
      builder.fee(json.fee);
    }
    if (json.fii != null) {
      builder.fii(json.fii);
    }
    if (json.url != null) {
      builder.url(json.url);
    }
    if (json.values != null) {
      builder.values(json.values);
    }
    return builder.build();
  }

  /**
   * Creates an immutable copy of a {@link FooDto} value.
   * Uses accessors to get values to initialize the new immutable instance.
   * If an instance is already immutable, it is returned as is.
   * @param instance The instance to copy
   * @return A copied immutable FooDto instance
   */
  public static ImmutableFooDto copyOf(FooDto instance) {
    if (instance instanceof ImmutableFooDto) {
      return (ImmutableFooDto) instance;
    }
    return ImmutableFooDto.builder()
        .from(instance)
        .build();
  }

  /**
   * Creates a builder for {@link ImmutableFooDto ImmutableFooDto}.
   * @return A new ImmutableFooDto builder
   */
  public static ImmutableFooDto.Builder builder() {
    return new ImmutableFooDto.Builder();
  }

  /**
   * Builds instances of type {@link ImmutableFooDto ImmutableFooDto}.
   * Initialize attributes and then invoke the {@link #build()} method to create an
   * immutable instance.
   * <p><em>{@code Builder} is not thread-safe and generally should not be stored in a field or collection,
   * but instead used immediately to create instances.</em>
   */
  public static final class Builder {
    private static final long INIT_BIT_TITLE = 0x1L;
    private static final long INIT_BIT_TECHNICAL_KEY = 0x2L;
    private static final long INIT_BIT_URL = 0x4L;
    private long initBits = 0x7L;
    private long optBits;

    private String fee;
    private String fii;
    private String url;
    private String[] values;

    private Builder() {
    }

    /**
     * Fill a builder with attribute values from the provided {@code FooDto} instance.
     * Regular attribute values will be replaced with those from the given instance.
     * Absent optional values will not replace present values.
     * Collection elements and entries will be added, not replaced.
     * @param instance The instance from which to copy values
     * @return {@code this} builder for use in a chained invocation
     */
    public final Builder from(FooDto instance) {
      Objects.requireNonNull(instance, "instance");
      fee(instance.getFee());
      fii(instance.getFii());
      url(instance.getUrl());
      values(instance.getValues());
      return this;
    }

    /**
     * Initializes the value for the {@link FooDto#getFee() fee} attribute.
     * @param fee The value for fee 
     * @return {@code this} builder for use in a chained invocation
     */
    public final Builder fee(String fee) {
      this.fee = Objects.requireNonNull(fee, "fee");
      initBits &= ~INIT_BIT_TITLE;
      return this;
    }

    /**
     * Initializes the value for the {@link FooDto#getFii() fii} attribute.
     * @param fii The value for fii 
     * @return {@code this} builder for use in a chained invocation
     */
    public final Builder fii(String fii) {
      this.fii = Objects.requireNonNull(fii, "fii");
      initBits &= ~INIT_BIT_TECHNICAL_KEY;
      return this;
    }

    /**
     * Initializes the value for the {@link FooDto#getUrl() url} attribute.
     * @param url The value for url 
     * @return {@code this} builder for use in a chained invocation
     */
    public final Builder url(String url) {
      this.url = Objects.requireNonNull(url, "url");
      initBits &= ~INIT_BIT_URL;
      return this;
    }

    /**
     * Initializes the value for the {@link FooDto#getValues() values} attribute.
     * <p><em>If not set, this attribute will have a default value as defined by {@link FooDto#getValues() values}.</em>
     * @param values The elements for values
     * @return {@code this} builder for use in a chained invocation
     */
    public final Builder values(String... values) {
      this.values = values.clone();
      return this;
    }

    /**
     * Builds a new {@link ImmutableFooDto ImmutableFooDto}.
     * @return An immutable instance of FooDto
     * @throws java.lang.IllegalStateException if any required attributes are missing
     */
    public ImmutableFooDto build() {
      if (initBits != 0) {
        throw new IllegalStateException(formatRequiredAttributesMessage());
      }
      return new ImmutableFooDto(this);
    }

    private String formatRequiredAttributesMessage() {
      List<String> attributes = new ArrayList<String>();
      if ((initBits & INIT_BIT_TITLE) != 0) attributes.add("fee");
      if ((initBits & INIT_BIT_TECHNICAL_KEY) != 0) attributes.add("fii");
      if ((initBits & INIT_BIT_URL) != 0) attributes.add("url");
      return "Cannot build FooDto, some of required attributes are not set " + attributes;
    }
  }

  private static <T> List<T> createSafeList(Iterable<? extends T> iterable, boolean checkNulls, boolean skipNulls) {
    ArrayList<T> list;
    if (iterable instanceof Collection<?>) {
      int size = ((Collection<?>) iterable).size();
      if (size == 0) return Collections.emptyList();
      list = new ArrayList<T>();
    } else {
      list = new ArrayList<T>();
    }
    for (T element : iterable) {
      if (skipNulls && element == null) continue;
      if (checkNulls) Objects.requireNonNull(element, "element");
      list.add(element);
    }
    return list;
  }

  private static <T> List<T> createUnmodifiableList(boolean clone, List<T> list) {
    switch(list.size()) {
    case 0: return Collections.emptyList();
    case 1: return Collections.singletonList(list.get(0));
    default:
      if (clone) {
        return Collections.unmodifiableList(new ArrayList<T>(list));
      } else {
        if (list instanceof ArrayList<?>) {
          ((ArrayList<?>) list).trimToSize();
        }
        return Collections.unmodifiableList(list);
      }
    }
  }
}
4

1 回答 1

1

我认为问题在于杰克逊找不到构建课程的方法。

这对我有用

import org.immutables.value.Value;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

@Value.Immutable
@Value.Style(privateNoargConstructor = true) //<<<< this is what you need I think
@JsonSerialize(as = ImmutableVal.class)
@JsonDeserialize(as = ImmutableVal.class)
interface Val {
    int a();

    @JsonProperty("b")
    String second();
}

和

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class ValMain {

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();
        String json = objectMapper.writeValueAsString(
            ImmutableVal.builder()
                .a(1)
                .second("B")
                .build());
        System.out.println(json);
        //{"a":1,"b":"B"}
        Val val = objectMapper.readValue(json, Val.class);
        System.out.println(val);
        //Val{a=1, second=B}
    }

}

然后你甚至可以摆脱 DTO

于 2021-06-28T17:14:34.597 回答