Question

我从这个link

获得Json

我正在使用以下两个pojo类进行映射。

1）NewsSource.class

    @JsonIgnoreProperties(ignoreUnknown = true)
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonPropertyOrder({ "id", "name", "description", "url", "category", "language", "country", "sortBysAvailable" })

    public class Source {

        @JsonProperty("id")
        private String id;
        @JsonProperty("name")
        private String name;
        @JsonProperty("description")
        private String description;
        @JsonProperty("url")
        private String url;
        @JsonProperty("category")
        private String category;
        @JsonProperty("language")
        private String language;
        @JsonProperty("country")
        private String country;
        @JsonProperty("sortBysAvailable")
        private List<String> sortBysAvailable = null;
//getter setters generated with IDE , and annotated with @JsonProperty too

2）Source.class

 public NewsSource getNewsSource() {
        String URL = source_url; //above mentioned url to get json
ObjectMapper omapper= new ObjectMapper();
        omapper.setVisibilityChecker(omapper.getSerializationConfig().getDefaultVisibilityChecker()
                .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));

   NewsSource newsSource =null;
        try {
        String result = restTemplate.getForObject(URL, String.class);
//result is returnning data properly
            omapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            newsSource = omapper.readValue(result, NewsSource.class);
//newsSource returnning null
}catch (Exception ex){

System.out.println("oooh exception ");
}

我正在使用此代码将json映射到pojo。

        <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
    </dependency>

我尝试过this链接中提到的许多建议技巧，但没有人为我工作：）

注意：我正在使用以下maven依赖杰克逊。

    private static Object getJsonObject(String str) {
        Object obj = null;
        try {
            ObjectMapper mapper = new ObjectMapper();
            mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            if (str != null) {
                obj = mapper.readValue(str, NewsSource.class);

            }
        } catch (Exception exc) {
            exc.printStackTrace();
        }
        System.out.println("json obj:===>" + obj);
        return obj;
    }

    public NewsSource getNewsSource() {
        String URL = source_url;

        NewsSource newsSource =null;
        try {
            String result = restTemplate.getForObject(URL, String.class);
            //String jsonStr=getJsonString(result);
            ObjectMapper mapper = new ObjectMapper();
        //    newsSource = mapper.readValue(result, NewsSource.class);

            newsSource= (NewsSource) getJsonObject(result);
            System.out.println("done:" +newsSource);
}catch (Exception ex){

System.out.println("oooh exception ");
}

        return newsSource;
    }

任何建议都将不胜感激。提前谢谢

更新我使用了以下代码。

    com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token
 at [Source: {"status":"ok","sources":[{"id":"abc-news-au","name":"ABC News (AU)","description":"Australia's most trusted source of local, national and world news. Comprehensive, independent, in-depth analysis, the latest business, sport, weather and more.","url":"http://www.abc.net.au/news","category":"general","language":"en","country":"au","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"al-jazeera-english","name":"Al Jazeera English","description":"News, analysis from the Middle East and worldwide, multimedia and interactives, opinions, documentaries, podcasts, long reads and broadcast schedule.","url":"http://www.aljazeera.com","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"ars-technica","name":"Ars Technica","description":"The PC enthusiast's resource. Power users and the tools they love, without computing religion.","url":"http://arstechnica.com","category":"technology","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"associated-press","name":"Associated Press","description":"The AP delivers in-depth coverage on the international, politics, lifestyle, business, and entertainment news.","url":"https://apnews.com/","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"bbc-news","name":"BBC News","description":"Use BBC News for up-to-the-minute news, breaking news, video, audio and feature stories. BBC News provides trusted World and UK news as well as local and regional perspectives. Also entertainment, business, science, technology and health news.","url":"http://www.bbc.co.uk/news","category":"general","language":"en","country":"gb","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"bbc-sport","name":"BBC Sport","description":"The home of BBC Sport online. Includes live sports coverage, breaking news, results, video, audio and analysis on Football, F1, Cricket, Rugby Union, Rugby League, Golf, Tennis and all the main world sports, plus major events such as the Olympic Games.","url":"http://www.bbc.co.uk/sport","category":"sport","language":"en","country":"gb","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"time","name":"Time","description":"Breaking news and analysis from TIME.com. Politics, world news, photos, video, tech reviews, health, science and entertainment news.","url":"http://time.com","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"usa-today","name":"USA Today","description":"Get the latest national, international, and political news at USATODAY.com.","url":"http://www.usatoday.com/news","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"}]}; line: 1, column: 402] (through reference chain: com.example.demo.dto.NewsSource["sources"]->java.util.ArrayList[0]->com.example.demo.dto.Source["sortBysAvailable"])
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.reportMappingException(DeserializationContext.java:1234)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1122)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1075)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.handleNonArray(StringCollectionDeserializer.java:260)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:187)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:177)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:20)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:287)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:259)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
    at com.example.demo.Utill.RuleUtill.getJsonObject(RuleUtill.java:80)
    at com.example.demo.Utill.RuleUtill.getNewsSource(RuleUtill.java:100)
    at com.example.demo.Service.NewsApiService.getSource(NewsApiService.java:32)
    at com.example.demo.Controller.Home.somespecific(Home.java:56)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
json obj:===>null
done:null

栈跟踪

public $default = array(
        'datasource' => 'Database/Postgres',
        'persistent' => false,
        'host'       => 'localhost',
        'login'      => 'my_db_user', 
        'password'   => 'my_db_passw', 
        'database'   => 'my_project_db', 
        'prefix'     => '',
        'encoding'   => 'utf8',
        'schema'     => 'postgres'
    );
public $other_schema = array(
        'datasource' => 'Database/Postgres',
        'persistent' => false,
        'host'       => 'localhost',
        'login'      => 'my_db_user', 
        'password'   => 'my_db_passw', 
        'database'   => 'my_project_db', 
        'prefix'     => '',
        'encoding'   => 'utf8',
        'schema'     => 'other_schema'
    );

Answer 1

由于某些原因，我修改了您的源代码：

RestTemplete将自动将响应Json字符串转换为您在NewsSource和Source中定义的指定POJO。
正如我上面所说，方法getJsonObject是多余的。
方法getNewsSource中的异常处理没有打印出真正的原因。

getNewsSource

public NewsSource getNewsSource() {
    String URL = source_url;

    NewsSource newsSource =null;
    try {
        /*
        String result = restTemplate.getForObject(URL, String.class);
        ObjectMapper mapper = new ObjectMapper();

        newsSource= (NewsSource) getJsonObject(result);
        System.out.println("done:" +newsSource);
        */

        newsSource = restTemplate.getForObject(URL, NewsSource.class);
        System.out.println("done:" + newsSource.toString());
    } catch (Exception ex){
        System.out.println("oooh exception \n" + ex);
    }

    return newsSource;
}

希望这对你有所帮助！：）

Answer 2

代码正常运行。看起来你正在使用杰克逊的旧版本。我测试了2.9.0及以下代码正在按预期工作，尽管2.9.0版本setVisibilityChecker（.....）已弃用。

public static void main(String[] args) {

    NewsSource nSource=new NewsSource();

    nSource.setStatus("status");

    Source source=new Source();

    source.setCategory("category");

    List<Source> sList=new ArrayList<Source>();
    sList.add(source);

    nSource.setSources(sList);

    String jsonStr=getJsonString(nSource);
    //{"status":"status","sources":[{"category":"category"}]}
    System.out.println(jsonStr);

    NewsSource newsSource =(NewsSource)getJsonObject(jsonStr);
    //NewsSource@1810399e
    System.out.println(newsSource);

}

private static String getJsonString(Object object) {
    String jsonString = "";
    try {
        ObjectMapper mapper = new ObjectMapper();
        if (object != null) {
            jsonString = mapper.writeValueAsString(object);
        }
    } catch (Exception exc) {
        exc.printStackTrace();
    }
    System.out.println("jsonString:===>" + jsonString);
    return jsonString;
}

private static Object getJsonObject(String str) {
    Object obj = null;
    try {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibilityChecker(mapper.getSerializationConfig().getDefaultVisibilityChecker()
                .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));

        mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        if (str != null) {
             obj = mapper.readValue(str, NewsSource.class);

        }
    } catch (Exception exc) {
        exc.printStackTrace();
    }
    System.out.println("json obj:===>" + obj);
    return obj;
}

Jackson Mapper在春季休息时返回null

2 个答案: