接口请求报错cannot deserialize from Object value

Lazy_T
2,724 阅读2分钟

异常信息：

2022-04-24 16:07:43 [http-nio-8080-exec-4] ERROR com.pagoda.config.MyExceptionHandler - 异常信息
org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class com.pagoda.bo.TagConditionsBo]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `TagConditionsBo` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (PushbackInputStream); line: 5, column: 9] (through reference chain: com.pagoda.bo.MaterialListBo["tagConditions"])
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:386)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:342)
	at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:185)
	at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:160)
	at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:133)
	at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
	at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:179)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:146)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at com.pagoda.config.PdWebFilter.doFilter(PdWebFilter.java:48)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1732)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `TagConditionsBo` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (PushbackInputStream); line: 5, column: 9] (through reference chain: com.pagoda.bo.MaterialListBo["tagConditions"])
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1904)
	at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400)
	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1349)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1415)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:351)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:184)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:313)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:176)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4674)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3682)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:378)
	... 46 common frames omitted

问题来源： 同事在某一次提交了一份代码，增加了以下功能： 有一个字段为Long类型，在返回前端时，尾部的几个数据变成0，导致数据报错，他增加这样一个配置用来将Long类型转化成为String类型

@EnableWebMvc
@Configuration
public class WebJsonConverterConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        MappingJackson2HttpMessageConverter jackson2HttpMessageConverter = new MappingJackson2HttpMessageConverter();
        ObjectMapper objectMapper = new ObjectMapper();
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
        simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
        objectMapper.registerModule(simpleModule);
        jackson2HttpMessageConverter.setObjectMapper(objectMapper);
        converters.add(jackson2HttpMessageConverter);
    }
}

异常原因： ObjectMapper在转化json为对象时，需要对象存在无参构造方法。而对象上增加了Lombok 的@Builder注解时，是不会增加无参构造方法的。

实验代码：

import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class Student {
    private String name;
    private int age;

}

编译之后：

public class Student {
    private String name;
    private int age;

    Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public static Student.StudentBuilder builder() {
        return new Student.StudentBuilder();
    }

    public String getName() {
        return this.name;
    }

    public int getAge() {
        return this.age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Student)) {
            return false;
        } else {
            Student other = (Student)o;
            if (!other.canEqual(this)) {
                return false;
            } else {
                Object this$name = this.getName();
                Object other$name = other.getName();
                if (this$name == null) {
                    if (other$name == null) {
                        return this.getAge() == other.getAge();
                    }
                } else if (this$name.equals(other$name)) {
                    return this.getAge() == other.getAge();
                }

                return false;
            }
        }
    }

    protected boolean canEqual(Object other) {
        return other instanceof Student;
    }

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $name = this.getName();
        int result = result * 59 + ($name == null ? 43 : $name.hashCode());
        result = result * 59 + this.getAge();
        return result;
    }

    public String toString() {
        return "Student(name=" + this.getName() + ", age=" + this.getAge() + ")";
    }

    public static class StudentBuilder {
        private String name;
        private int age;

        StudentBuilder() {
        }

        public Student.StudentBuilder name(String name) {
            this.name = name;
            return this;
        }

        public Student.StudentBuilder age(int age) {
            this.age = age;
            return this;
        }

        public Student build() {
            return new Student(this.name, this.age);
        }

        public String toString() {
            return "Student.StudentBuilder(name=" + this.name + ", age=" + this.age + ")";
        }
    }
}

单独使用@Data时是会创建对象无参构造方法的，加上@Builder之后，无参构造就没了 并且在对象内手动增加无参构造编译也不通过

image.png

解决方法： 1，使用@Tolerate 增加一个构造方法，在构造方法上增加注解，这是lombok提供的一个冲突兼容方式

import lombok.Builder;
import lombok.Data;
import lombok.experimental.Tolerate;

@Data
@Builder
public class Student {
    private String name;
    private int age;

    @Tolerate
    public Student() {
    }
}

2，调整@Builder的位置至构造方法上 这是官方提供的另一种解法 projectlombok.org/features/Bu…

image.png

import lombok.Builder;
import lombok.Data;

@Data
public class Student {
    private String name;
    private int age;

    @Builder
    public Student() {
    }
}

@Builder可以添加在方法上，添加在构造方法上，可以实现和添加在类上同样的效果，并且兼容了无参构造方法 @Builder增加在普通方法上，好像没啥大用处

import lombok.Builder;
import lombok.Data;

@Data
public class Student {
    private String name;
    private int age;

    @Builder
    public void calcAge() {

    }
}

public class Student {
    private String name;
    private int age;

    public void calcAge() {
    }

    //主要是生成了这个方法
    public entity.Student.VoidBuilder builder() {
        return new entity.Student.VoidBuilder(this);
    }

    public Student() {
    }

    public String getName() {
        return this.name;
    }

    public int getAge() {
        return this.age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Student)) {
            return false;
        } else {
            Student other = (Student)o;
            if (!other.canEqual(this)) {
                return false;
            } else {
                Object this$name = this.getName();
                Object other$name = other.getName();
                if (this$name == null) {
                    if (other$name == null) {
                        return this.getAge() == other.getAge();
                    }
                } else if (this$name.equals(other$name)) {
                    return this.getAge() == other.getAge();
                }

                return false;
            }
        }
    }

    protected boolean canEqual(Object other) {
        return other instanceof Student;
    }

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $name = this.getName();
        int result = result * 59 + ($name == null ? 43 : $name.hashCode());
        result = result * 59 + this.getAge();
        return result;
    }

    public String toString() {
        return "Student(name=" + this.getName() + ", age=" + this.getAge() + ")";
    }
}
avatar
文章
阅读
粉丝