我正在尝试使用Jakson库将以下JSON响应绑定到对象，但它返回java.lang.NullPointerException。
响应
{"region":
{"span":
{"latitude_delta": 0.10262262794520893, "longitude_delta": 0.22282942},
"center": {"latitude": 51.510372893357001, "longitude": -0.1108336}},
"total": 246,
"businesses": [
{"is_claimed": false,
"rating": 4.5,
"mobile_url": "http://m.yelp.co.uk/biz/r-garcia-and-sons-foods-and-wines-of-spain-london",
"rating_img_url": "http://s3-media2.ak.yelpcdn.com/assets/2/www/img/99493c12711e/ico/stars/v1/stars_4_half.png",
"review_count": 11,
"name": "R Garcia \u0026 Sons - Foods and Wines of Spain",
"snippet_image_url": "http://s3-media2.ak.yelpcdn.com/photo/8xquccU5FKaFg9ZlANdOJA/ms.jpg",
"rating_img_url_small": "http://s3-media2.ak.yelpcdn.com/assets/2/www/img/a5221e66bc70/ico/stars/v1/stars_small_4_half.png",
"url": "http://www.yelp.co.uk/biz/r-garcia-and-sons-foods-and-wines-of-spain-london",
"phone": "+442072216119",
"snippet_text": "aka R Garcia \u0026 Son, and Cafe Garcia. Although, technically, Cafe Garcia is next door attached to their la carniceria. \n\nIt is a great Spanish grocery store...",
"image_url": "http://s3-media3.ak.yelpcdn.com/bphoto/t14haXQrAW8HMwc0RTL1jQ/ms.jpg",
"categories": [["Delis", "delis"], ["Spanish", "spanish"], ["Beer, Wine \u0026 Spirits", "beer_and_wine"]],
"display_phone": "+44 20 7221 6119",
"rating_img_url_large": "http://s3-media4.ak.yelpcdn.com/assets/2/www/img/9f83790ff7f6/ico/stars/v1/stars_large_4_half.png",
"id": "r-garcia-and-sons-foods-and-wines-of-spain-london",
"is_closed": false,
"location":
{"city": "London",
"display_address": ["248-250 Portobello Road", "Notting Hill", "London W11 1LL", "UK"],
"neighborhoods": ["Notting Hill"],
"postal_code": "W11 1LL",
"country_code": "GB",
"address": ["248-250 Portobello Road"],
"state_code": "XGL"}
},
{"is_claimed": false, "rating": 3.0, ......
我的对象
public class Response {
private Region region;
private int total;
private List<Businesses> businesses = null;
public Response() {
this.businesses = new ArrayList();
}
public Region getRegion() {
return region;
}
public void setRegion(Region region) {
this.region = region;
}
public int getTotal() {
return total;
}
public void setTotal(int total) {
this.total = total;
}
public List<Businesses> getBusinesses() {
return businesses;
}
public void setBusinesses(List<Businesses> businesses) {
this.businesses = businesses;
}
}
业务类
public class Businesses {
private boolean is_claimed;
private double rating;
private String mobile_url;
private String rating_img_url;
private int review_count;
private String name;
private String snippet_image_url;
private String rating_img_url_small;
private String url;
private String phone;
private String snippet_text;
private String image_url;
private String[] categories;
private String display_phone;
private String rating_img_url_large;
private String id;
private boolean is_closed;
private Location location = null;
public Businesses() {
this.location = new Location();
}
public boolean isIs_claimed() {
return is_claimed;
}
public void setIs_claimed(boolean is_claimed) {
this.is_claimed = is_claimed;
}
public double getRating() {
return rating;
}
public void setRating(double rating) {
this.rating = rating;
}
public String getMobile_url() {
return mobile_url;
}
public void setMobile_url(String mobile_url) {
this.mobile_url = mobile_url;
}
public String getRating_img_url() {
return rating_img_url;
}
public void setRating_img_url(String rating_img_url) {
this.rating_img_url = rating_img_url;
}
public int getReview_count() {
return review_count;
}
public void setReview_count(int review_count) {
this.review_count = review_count;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSnippet_image_url() {
return snippet_image_url;
}
public void setSnippet_image_url(String snippet_image_url) {
this.snippet_image_url = snippet_image_url;
}
public String getRating_img_url_small() {
return rating_img_url_small;
}
public void setRating_img_url_small(String rating_img_url_small) {
this.rating_img_url_small = rating_img_url_small;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getSnippet_text() {
return snippet_text;
}
public void setSnippet_text(String snippet_text) {
this.snippet_text = snippet_text;
}
public String getImage_url() {
return image_url;
}
public void setImage_url(String image_url) {
this.image_url = image_url;
}
public String[] getCategories() {
return categories;
}
public void setCategories(String[] categories) {
this.categories = categories;
}
public String getDisplay_phone() {
return display_phone;
}
public void setDisplay_phone(String display_phone) {
this.display_phone = display_phone;
}
public String getRating_img_url_large() {
return rating_img_url_large;
}
public void setRating_img_url_large(String rating_img_url_large) {
this.rating_img_url_large = rating_img_url_large;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public boolean isIs_closed() {
return is_closed;
}
public void setIs_closed(boolean is_closed) {
this.is_closed = is_closed;
}
public Location getLocation() {
return location;
}
public void setLocation(Location location) {
this.location = location;
}
}
位置等级
public class Location {
private String city;
private String[] display_address;
private String[] neighborhoods;
private String postal_code;
private String country_code;
private String[] address;
private String state_code;
public Location() {
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String[] getDisplay_address() {
return display_address;
}
public void setDisplay_address(String[] display_address) {
this.display_address = display_address;
}
public String[] getNeighborhoods() {
return neighborhoods;
}
public void setNeighborhoods(String[] neighborhoods) {
this.neighborhoods = neighborhoods;
}
public String getPostal_code() {
return postal_code;
}
public void setPostal_code(String postal_code) {
this.postal_code = postal_code;
}
public String getCountry_code() {
return country_code;
}
public void setCountry_code(String country_code) {
this.country_code = country_code;
}
public String[] getAddress() {
return address;
}
public void setAddress(String[] address) {
this.address = address;
}
public String getState_code() {
return state_code;
}
public void setState_code(String state_code) {
this.state_code = state_code;
}
}
异常
SEVERE: org.codehaus.jackson.map.JsonMappingException:
(was java.lang.NullPointerException) (through reference chain:
com.myproject.restaurant.yelp.Response["businesses"])
at org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:218)
at org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:183)
at org.codehaus.jackson.map.deser.BeanDeserializer.wrapAndThrow(BeanDeserializer.java:1472)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:699)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2732)
at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1909)
at com.myproject.controller.Restaurants.Yelp(Restaurants.java:93)
at com.myproject.controller.Restaurants.find(Restaurants.java:32)
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 com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488)
at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzl
SEVERE: y.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.NullPointerException
at org.codehaus.jackson.map.deser.impl.BeanPropertyMap.find(BeanPropertyMap.java:80)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:694)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:194)
at org.codehaus.jackson.map.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:30)
at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299)
at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:414)
at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:697)
... 86 more
我的绑定代码
InputStream response = yelp.search("spanish+food", "London");
ObjectMapper mapper = new ObjectMapper();
Response responseObj= mapper.readValue(response, Response.class);
System.err.println(">" + responseObj.getRegion().getSpan().getLatitude_delta());
答案 0 :(得分：3)
以下JSON字符串：
"categories": [["Delis", "delis"], ["Spanish", "spanish"], ["Beer, Wine \u0026 Spirits", "beer_and_wine"]],
未映射到
private String[] categories;
JSON categories是一个字符串列表列表，而您只是将其映射到一维字符串数组。
要么尝试二维数组，要么最好使用List<List<String>>。