com.fasterxml.jackson.databind.JsonMappingException: 无法构造 : poja 的实例 class 找不到合适的构造函数
com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of : poja class no suitable constructor found
这是 ApiError 的 POJO class。我正在尝试将字符串转换为以下 class。我正在将 {"message": "success", "code":"403"} 字符串传递给 convertToObject 方法。
package com.wrapper.reply;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Builder;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
@Getter
@Builder
@RequiredArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public final class ApiError {
private final String code;
private final String message;
}
public static <T> T convertToObject(String body, Class<T> clazz) {
try {
ObjectMapper mapper = new ObjectMapper();
return mapper.readValue(body, clazz);
} catch (IOException e) {
log.error(ERRMSG_PARSE_JSON, e);
throw new BadRequestException(ERRMSG_PARSE_JSON, e);
}
}
但是我在尝试这样做时遇到以下错误。
12:58:44.458 [main] ERROR com.JsonUtil - Exception in parsing json string
com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
at com.JsonUtil.convertToObject(JsonUtil.java:62)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=13=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
com.exception.BadRequestException: Exception in parsing json string
at com.JsonUtil.convertToObject(JsonUtil.java:65)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=13=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
at com.JsonUtil.convertToObject(JsonUtil.java:62)
... 28 more
Disconnected from the target VM, address: '127.0.0.1:56545', transport: 'socket'
Process finished with exit code 255
更新:
似乎 Jackson 默认情况下会尝试在创建对象实例后设置值,如果 class 具有 final
字段,这是不可能的。
所以,我们需要定义一个构造函数,并用@JsonCreator
注释来告诉Jackson使用构造函数反序列化。
@Getter
@Builder
//@RequiredArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
class ApiError {
private final String code;
private final String message;
@JsonCreator
public ApiError(@JsonProperty("code") String code, @JsonProperty("message") String message) {
this.code = code;
this.message = message;
}
}
Jackson 无法找到实例化 ApiError
对象并为其设置值的方法。
您需要对 ApiError
class.
进行以下任何 一项 更改
- 用
@JsonPOJOBuilder(withPrefix = "")
注释
- 添加 setter 方法(或 lombok
@Setter
)
- 添加参数化构造函数(或 lombok
@AllArgsConstructor
)
缺少默认构造函数或创建者
@NoArgsConstructor
这是 ApiError 的 POJO class。我正在尝试将字符串转换为以下 class。我正在将 {"message": "success", "code":"403"} 字符串传递给 convertToObject 方法。
package com.wrapper.reply;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Builder;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
@Getter
@Builder
@RequiredArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public final class ApiError {
private final String code;
private final String message;
}
public static <T> T convertToObject(String body, Class<T> clazz) {
try {
ObjectMapper mapper = new ObjectMapper();
return mapper.readValue(body, clazz);
} catch (IOException e) {
log.error(ERRMSG_PARSE_JSON, e);
throw new BadRequestException(ERRMSG_PARSE_JSON, e);
}
}
但是我在尝试这样做时遇到以下错误。
12:58:44.458 [main] ERROR com.JsonUtil - Exception in parsing json string
com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
at com.JsonUtil.convertToObject(JsonUtil.java:62)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=13=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
com.exception.BadRequestException: Exception in parsing json string
at com.JsonUtil.convertToObject(JsonUtil.java:65)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=13=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
at com.JsonUtil.convertToObject(JsonUtil.java:62)
... 28 more
Disconnected from the target VM, address: '127.0.0.1:56545', transport: 'socket'
Process finished with exit code 255
更新:
似乎 Jackson 默认情况下会尝试在创建对象实例后设置值,如果 class 具有 final
字段,这是不可能的。
所以,我们需要定义一个构造函数,并用@JsonCreator
注释来告诉Jackson使用构造函数反序列化。
@Getter
@Builder
//@RequiredArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
class ApiError {
private final String code;
private final String message;
@JsonCreator
public ApiError(@JsonProperty("code") String code, @JsonProperty("message") String message) {
this.code = code;
this.message = message;
}
}
Jackson 无法找到实例化 ApiError
对象并为其设置值的方法。
您需要对 ApiError
class.
- 用
@JsonPOJOBuilder(withPrefix = "")
注释 - 添加 setter 方法(或 lombok
@Setter
) - 添加参数化构造函数(或 lombok
@AllArgsConstructor
)
缺少默认构造函数或创建者
@NoArgsConstructor