我有以下测试班：
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.ibm.cio.cloud.cost.model.ElasticResponse;
import com.jayway.jsonpath.JsonPath;
@JsonIgnoreProperties(ignoreUnknown = true)
public class TestJSONPaths {
private static final String json = "{\"hits\":{\"total\":1,\"hits\":[{\"_id\":\"oEE4j2QBXCNPxFWHqq3i\",\"_score\":1.0,\"_source\":{\"status\":\"SUCCESSFUL\",\"reason\":\"OK, Single ACTIVE status can process\"}}]}}";
public static void main(String[] args) {
List<String> strippedJSON = JsonPath.read(json, "$.hits.hits._source");
ElasticResponse response = null;
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
mapper.configure(DeserializationFeature.USE_JAVA_ARRAY_FOR_JSON_ARRAY, true);
try {
System.out.println("From this json string:" + strippedJSON + "\n");
response = mapper.readValue(strippedJSON.toString(), ElasticResponse.class);
System.out.println("ElasticDocument=" + mapper.writerWithDefaultPrettyPrinter().writeValueAsString(response.getDocuments()));
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
这是ElasticResponse类的定义：
public class ElasticResponse {
private List<ElasticDocument> documents;
public List<ElasticDocument> getDocuments() {
return documents;
}
public void setDocuments(List<ElasticDocument> documents) {
this.documents = documents;
}
}
public class ElasticDocument {
private String _id;
private String status;
private String reason;
... getters/setters
}
我正在尝试从给定的JSON映射一个ElasticDocument对象，但它在下面引发了以下错误。我试图将JSON过滤为：[{_source document values}]。此错误发生在Main类的第一行。我该如何映射这个Json？
[DEBUG] Evaluating path: $['hits']['hits']['_source']
Exception in thread "main" com.jayway.jsonpath.PathNotFoundException: Expected to find an object with property ['_source'] in path $['hits']['hits'] but found 'net.minidev.json.JSONArray'. This is not a json object according to the JsonProvider: 'com.jayway.jsonpath.spi.json.JsonSmartJsonProvider'.
at com.jayway.jsonpath.internal.path.PropertyPathToken.evaluate(PropertyPathToken.java:71)
at com.jayway.jsonpath.internal.path.PathToken.handleObjectProperty(PathToken.java:81)
at com.jayway.jsonpath.internal.path.PropertyPathToken.evaluate(PropertyPathToken.java:79)
at com.jayway.jsonpath.internal.path.PathToken.handleObjectProperty(PathToken.java:81)
at com.jayway.jsonpath.internal.path.PropertyPathToken.evaluate(PropertyPathToken.java:79)
at com.jayway.jsonpath.internal.path.RootPathToken.evaluate(RootPathToken.java:62)
at com.jayway.jsonpath.internal.path.CompiledPath.evaluate(CompiledPath.java:53)
at com.jayway.jsonpath.internal.path.CompiledPath.evaluate(CompiledPath.java:61)
at com.jayway.jsonpath.JsonPath.read(JsonPath.java:187)
at com.jayway.jsonpath.internal.JsonContext.read(JsonContext.java:102)
at com.jayway.jsonpath.internal.JsonContext.read(JsonContext.java:89)
at com.jayway.jsonpath.JsonPath.read(JsonPath.java:502)
at com.ibm.cio.cloud.cost.TestJSONPaths.main(TestJSONPaths.java:18)
答案 0 :(得分：1)
该异常是由于jsonpath返回一个数组而不是一个对象，因此，如果您将jsonpath修复为如下所示：
$.hits.hits[*]._source
然后它将正确评估。但是，这可能仍然无法实现您想要的功能。.JsonPath.read()将为您反序列化JSON。但是您必须注意这一点：
public class Test {
private static final String json = "{\"hits\":{\"total\":1,\"hits\":[{\"_id\":\"oEE4j2QBXCNPxFWHqq3i\",\"_score\":1.0,\"_source\":{\"status\":\"SUCCESSFUL\",\"reason\":\"OK, Single ACTIVE status can process\"}}]}}";
public static void main(String[] args) {
List<ElasticDocument> docs = JsonPath.read(json, "$.hits.hits[*]._source");
System.out.println("elasticDoc: " + docs.get(0));
}
public static class ElasticDocument {
public String _id;
public String status;
public String reason;
@Override
public String toString() {
return "ElasticDocument{" +
"_id='" + _id + '\'' +
", status='" + status + '\'' +
", reason='" + reason + '\'' +
'}';
}
}
}
它看起来很有效，但是docs List现在实际上是List中的Map个。显然可以在Jackson上注册JsonPath，但我无法使其工作
或者，您可以使用Jackson来反序列化JSON，然后应该创建一个与json结构匹配的对象模型，然后可以使用ObjectMapper来进行反序列化
public class Test {
private static final String json = "{\"hits\":{\"total\":1,\"hits\":[{\"_id\":\"oEE4j2QBXCNPxFWHqq3i\",\"_score\":1.0,\"_source\":{\"status\":\"SUCCESSFUL\",\"reason\":\"OK, Single ACTIVE status can process\"}}]}}";
public static void main(String[] args) {
System.out.println("From this json string:" + json + "\n");
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
mapper.configure(DeserializationFeature.USE_JAVA_ARRAY_FOR_JSON_ARRAY, true);
try {
HitsResource hitsResource = mapper.readValue(json, HitsResource.class);
System.out.println("jackson elasticDoc: " + hitsResource.hitsParent.hits.get(0).source);
} catch (Exception e) {
e.printStackTrace();
}
}
public static class HitsResource {
@JsonProperty("hits")
public HitsParent hitsParent;
@Override
public String toString() {
return "HitsResource{" +
"hitsParent=" + hitsParent +
'}';
}
}
public static class HitsParent {
@JsonProperty("total")
public Long total;
@JsonProperty("hits")
public List<Hits> hits;
@Override
public String toString() {
return "HitsParent{" +
"total=" + total +
", hits=" + hits +
'}';
}
}
public static class Hits {
@JsonProperty("_id")
public String id;
@JsonProperty("_score")
public BigDecimal score;
@JsonProperty("_source")
public ElasticDocument source;
@Override
public String toString() {
return "Hits{" +
"id='" + id + '\'' +
", score=" + score +
", source=" + source +
'}';
}
}
public static class ElasticDocument {
@JsonProperty("_id")
public String _id;
@JsonProperty("status")
public String status;
@JsonProperty("reason")
public String reason;
@Override
public String toString() {
return "ElasticDocument{" +
"_id='" + _id + '\'' +
", status='" + status + '\'' +
", reason='" + reason + '\'' +
'}';
}
}
}