问题描述
以下场景。
具有以下类的小 SpringBoot 应用程序：
食物：
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",{
"fee":"4711_MESSAGE","fii":"4711_TECH_MESSAGE","url":"/4711","values":[
]
}
]
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，因为以下代码行使用其中的数据创建 Object：
return Arrays.asList(objectMapper.readValue(jsonFile,Object[].class));
我还尝试在 @Value.Style(builder = "new") 处使用 FooDto.class，如下所示：https://immutables.github.io/json.html
- 杰克逊：2.12.3
- org.immutables: 2.8.2
编辑：
根据使用 Builder 的 ImmutableDTO 的要求：
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.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.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,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);
}
}
}
}
解决方法
我认为问题在于 jackson 找不到构建类的方法。
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