无法反序列化 java.util.ArrayList 的实例，START_OBJECT令牌

java spring jackson jax-rs resteasy

2022-08-31 07:10:07

我正在尝试发布自定义对象。我在请求正文中的 JSON 是这样的：List

{
    "collection": [
        {
            "name": "Test order1",
            "detail": "ahk ks"
        },
        {
            "name": "Test order2",
            "detail": "Fisteku"
        }
    ]
}

处理请求的服务器端代码：

import java.util.Collection;

import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;


@Path(value = "/rest/corder")
public class COrderRestService {

    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    public Response postOrder(Collection<COrder> orders) {
        StringBuilder stringBuilder = new StringBuilder();
        for (COrder c : orders) {
            stringBuilder.append(c.toString());
        }
        System.out.println(stringBuilder);
        return Response.ok(stringBuilder, MediaType.APPLICATION_JSON).build();
    }
}

实体：COrder

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class COrder {
    String name;
    String detail;

    @Override
    public String toString() {
        return "COrder [name=" + name + ", detail=" + detail
                + ", getClass()=" + getClass() + ", hashCode()=" + hashCode()
                + ", toString()=" + super.toString() + "]";
    }
}

但会引发异常：

SEVERE: Failed executing POST /rest/corder
org.jboss.resteasy.spi.ReaderException: org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: org.apache.catalina.connector.CoyoteInputStream@6de8c535; line: 1, column: 1]
    at org.jboss.resteasy.core.MessageBodyParameterInjector.inject(MessageBodyParameterInjector.java:183)
    at org.jboss.resteasy.core.MethodInjectorImpl.injectArguments(MethodInjectorImpl.java:88)
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:111)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:280)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:234)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:221)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:356)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:179)
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:220)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:724)

答案 1

问题是 JSON - 默认情况下，这不能反序列化为 a，因为它实际上不是 JSON 数组 - 如下所示：Collection

[
    {
        "name": "Test order1",
        "detail": "ahk ks"
    },
    {
        "name": "Test order2",
        "detail": "Fisteku"
    }
]

由于您没有控制反序列化的确切过程（RestEasy确实如此）， 因此第一种选择是简单地将JSON作为a注入，然后控制反序列化过程：String

Collection<COrder> readValues = new ObjectMapper().readValue(
    jsonAsString, new TypeReference<Collection<COrder>>() { }
);

你会失去一些不必自己做的那种便利，但你很容易解决问题。

另一种选择 - 如果您无法更改JSON - 将构造一个包装器以适合您的JSON输入的结构 - 并使用它而不是.Collection<COrder>

希望这有帮助。

答案 2

您可以更新 ObjectMapper 对象，而不是 JSON 文档，如下所示：

ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);