xml - 使用 Jackson : no String-argument constructor/factory method to deserialize from String value 从 XML 到 POJO 的反序列化问题

Question

我有一个 XML 文档，我需要将其转换(反序列化)为 Java POJO。我无法更改 XML 文档的结构。我使用 Java 8 和 Jackson 框架进行映射。Gradle 依赖项:

dependencies {
    compile('com.fasterxml.jackson.dataformat:jackson-dataformat-xml')
    compile('org.springframework.boot:spring-boot-starter-freemarker')
    compile('org.springframework.boot:spring-boot-starter-web')
    providedRuntime('org.springframework.boot:spring-boot-starter-tomcat')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

包装器 XML 文档:

@JacksonXmlRootElement(localName = "rates_response")
public class RatesResponse implements Serializable{
    private static final long serialVersionUID = 3254688495454519L;

    @JacksonXmlProperty(isAttribute = true)
    private String b_number = "";

    @JacksonXmlProperty(isAttribute = true)
    private String l_premium = "";

    @JacksonXmlProperty(isAttribute = true)
    private String currency = "";

    @XmlElement(required = false)
    @JacksonXmlProperty
    private String c_b_relationship = null;

    @JacksonXmlProperty(isAttribute = true)
    private String n_of_p_loans = null;

    /*
     * Key: status_code
     * Key: status_explanation
     */
    @JacksonXmlElementWrapper
    private Map<String, String> message_status = null;

   // @XmlElement
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<RateDetails> rate_details = null;

    public RatesResponse(){}
     //GETTERS/SETTERS
Child document (`List<RateDetails> rate_details = null;`):


@JacksonXmlRootElement(localName = "rate_details")
public class RateDetails implements Serializable {
    private static final long serialVersionUID = 324564684815158619L;

    @JacksonXmlProperty
    private String r_reference = null;
    @JacksonXmlProperty
    private String n_of_p_days = null;
    @JacksonXmlProperty
    private String n_of_instalments = null;
    @JacksonXmlProperty
    private String n_rate = null;
    @JacksonXmlProperty
    private String p_p_available = null;

    @XmlElement(required = false)
    @JacksonXmlProperty
    private String i_overrider = null;//not always appears in doc
    @JacksonXmlProperty
    private String a_fee = null;
    @JacksonXmlProperty
    private String m_fee = null;
    @JacksonXmlProperty
    private String t_fees = null;
    @JacksonXmlProperty
    private String t_c_for_credit = null;
    @JacksonXmlProperty
    private String d_amount = null;
    @JacksonXmlProperty
    private String apr = null;

    public RateDetails(){}
    //GETTERS/SETTERS

要解析的 XML 文档:

<?xml version="1.0"?>
<!DOCTYPE rates_response SYSTEM "p_f_interface.dtd">
<rates_response b_number="KK5000000000" l_premium="5000.00" currency="GBP" >
    <message_status>
        <status_code>1000</status_code>
        <status_explanation>Success</status_explanation>
    </message_status>
    <c_b_relationship n_of_p_loans="0"/>
    <rate_details>
        <r_reference>AS28</r_reference>
        <n_of_p_days>28</n_of_p_days>
        <n_of_instalments>12</n_of_instalments>
        <n_rate>7.00</n_rate>
        <p_p_available>NO</p_p_available>
        <i_overrider>3.65</i_overrider>
        <a_fee>0.00</a_fee>
        <m_fee>0.00</m_fee>
        <t_fees>0.00</t_fees>
        <t_c_for_credit>350.00</t_c_for_credit>
        <d_amount>0.00</d_amount>
        <apr>16.05</apr>
    </rate_details>    
</rates_response>

解析文档的方法:

private RatesResponse readRatesDoc() {
    RatesResponse xmlContainer = null;

    ObjectMapper xmlMapper = new XmlMapper();
    try {
        xmlContainer = xmlMapper.readValue(contrUtil.readXmlFile("Rates_Response.xml"), RatesResponse.class);
    } catch (IOException e) {
        log.log(Level.SEVERE, "An Exception on parsing XML document", e);
    }
    return xmlContainer;
}

异常:

com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of premium.finance.beanResponse.rates.RateDetails: no String-argument constructor/factory method to deserialize from String value ('16.05')
 at [Source: java.io.StringReader@7bd22d0b; line: 1, column: 945] (through reference chain: premium.finance.beanResponse.rates.RatesResponse["rate_details"]->java.util.ArrayList[1])
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:261) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:366) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:307) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1278) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:159) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:150) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:277) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:499) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:101) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer.deserialize(WrapperHandlingDeserializer.java:120) ~[jackson-dataformat-xml-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789) ~[jackson-databind-2.8.3.jar:2.8.3]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2833) ~[jackson-databind-2.8.3.jar:2.8.3]
    at premium.finance.controller.IndexController.readRatesDoc(IndexController.java:190) [main/:na]
    at premium.finance.controller.IndexController.requestIndex(IndexController.java:69) [main/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_91]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_91]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_91]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_91]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:89) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1410) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_91]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_91]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_91]

顶行说:

no String-argument constructor/factory method to deserialize from String value ('16.05')

它所指的值来自这个标签下:

<apr>16.05</apr>

如果我替换(四处移动)标记 <apr>16.05</apr> ，解析器会工作并且不会导致异常。如果我用不同的标签替换标签，仍然会出现相同的异常； 出于某些原因，它仅影响 <rate_details> 包装器标记中的最后一个标记。

可能是什么问题？

Answer 1

版本 2.10.2 仍然存在这个问题，以下版本为我修复了它。

替换:

ObjectMapper xmlMapper = new XmlMapper();

与:

JacksonXmlModule module = new JacksonXmlModule();
module.setDefaultUseWrapper(false);
XmlMapper xmlMapper = new XmlMapper(module);

来源:

https://github.com/FasterXML/jackson-dataformat-xml/issues/219#issuecomment-286003056