JavaRESTlet将JSON转换为LinkedHashMap，而不是List<MyObject>？

Question

这就是我的Rest端点的样子

  @Post("json")
  public List<LogProcessorExpression> addLogProcessorExpression(
      final List<LogProcessorExpression> expressions) throws LPRestletException {
    if (expressions == null || expressions.isEmpty()) {
      return Collections.emptyList();
    }

    final Integer currentTenantId = Utils.getCurrentTenantId(getRequest());
    return customAttributesManager.addLogProcessorExpression(currentTenantId, expressions);
  }

它调用的方法看起来像

List<LogProcessorExpression> addLogProcessorExpression(final Integer currentTenantId,
                                                       final List<LogProcessorExpression> expressions)
      throws LPRestletException {
    final Map<String, LogProcessorExpression> cache = getCacheByCustomAttributeName(expressions);
    try {
      final List<Customattributesmetadata> cams =
          getCustomAttributesMetaDataForTenant(currentTenantId);

      for (final Customattributesmetadata metadata : cams) {
        if (cache.containsKey(metadata.getAttributecolumnname())) {
          metadata.setLogprocessorexpression(
              cache.get(metadata.getAttributecolumnname()).toString());
        }
        metadata.save();
      }
    } catch (final TorqueException e) {
      final String error = "Failed to update LogExpression custom attributes";
      LOGGER.error(error, e);
      throw new LPRestletException(error, e);
    }

    return expressions;
  }

调用链中的其他方法。当我以

 curl -v -H "Authorization:Basic Y3VyYasqrwqrjQGdtYWlsLmNvbTp0YXAzYWg=" \
     -H "Content-Type:application/json" \
     -d '[{"source": "ad", "attributePrefix": "ad_", "attributeName": "department"}]' \
     http://172.11.041.240:8080/api/rest/msp/attributes

它回来了

{
   "code" : 500
   "message" : "The server encountered an unexpected condition which prevented it from fulfilling the request",
}

当我看这些日志时，我看到的是

        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.shn.api.dto.LogProcessorExpression
        at com.shn.api.restlet.logprocessor.CustomAttributesManager.getCacheByCustomAttributeName(CustomAttributesManager.java:55)
        at com.shn.api.restlet.logprocessor.CustomAttributesManager.addLogProcessorExpression(CustomAttributesManager.java:24)
        at com.shn.api.restlet.logprocessor.CustomAttributeMetadataRestlet.addLogProcessorExpression(CustomAttributeMetadataRestlet.java:44)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.restlet.resource.ServerResource.doHandle(ServerResource.java:521)
        ... 67 more

问题
-为什么它不把它们投给List<LogProcessorExpression>
-我需要做什么来修复它

更新

第24行看起来像

final Map<String, LogProcessorExpression> cache = getCacheByCustomAttributeName(expressions);  

第44行看起来像

return customAttributesManager.addLogProcessorExpression(currentTenantId, expressions);  

getCacheByCustomAttributeName(expressions)看起来像

  Map<String, LogProcessorExpression> getCacheByCustomAttributeName(
      final List<LogProcessorExpression> expressions) {
    if (expressions == null || expressions.isEmpty()) {
      return Collections.emptyMap();
    }

    final Map<String, LogProcessorExpression> attributeByExpression = new HashMap<>();
    for (final LogProcessorExpression expression : expressions) {
      attributeByExpression.put(expression.getAttributeName(), expression);
    }
    return attributeByExpression;
  }

Answer 1

我认为restlet可能不够复杂，无法从处理程序方法的参数列表中提取参数化类型List<LogProcessorExpression>

@Post("json")
public List<LogProcessorExpression> addLogProcessorExpression(
  final List<LogProcessorExpression> expressions)

它只需要List并且在反序列化（与Jackson一起）时可能会使用它。Jackson使用LinkedHashMap作为反序列化目标类型（如果没有提供）

如果restlet不能更好地实现这一点（可能是在更新的版本中？），一个潜在的解决方案是定义一个自定义类型

class LogProcessorExpressionList extends ArrayList<LogProcessorExpression> {}

并使用该类型作为参数类型

@Post("json")
public List<LogProcessorExpression> addLogProcessorExpression(
  final LogProcessorExpressionList expressions)

Jackson然后可以提取类型LogProcessorExpressionList的参数化超类型，即ArrayList<LogProcessorExpression>，从中可以提取LogProcessorExpression作为目标元素类型

Answer 2

也许你能用一个定制的杰克逊反序列化器来实现这个？有关此功能，请参见此链接：http://www.baeldung.com/jackson-deserialization

这个答案为您提供了一些配置Jackson ObjectMapper:How to register Jackson Jdk8 module in Restlet的提示。这允许注册自定义反序列化程序，并进行反序列化处理，以便在列表中创建正确的对象

希望对你有帮助， 蒂埃里

Answer 3

这对我来说很有用

class LogProcessorExpressionList extends ArrayList<LogProcessorExpression> {}