Java:Jackson 数据绑定(bind)无法从 JSON 文件映射整个类

Question

我正在尝试将 JSON 文件映射到名为 Tweets.java 的 java 类，并且我能够绑定(bind)和检索 JSON 文件的第一部分(tweet 类)中的数据，但 Jackson ObjectMapper 无法映射 Tweets.Java 的嵌套类(用户类和实体类)。

这是我访问 JSON 绑定(bind)到的类的方法:

WeatherDatabaseCreator.java

    //Read in files to be parsed.
    for (int i = 0; i < twitterFiles.size(); i++) {

        File twitterFile = twitterFiles.get(i);
        WeatherTweetParser wtp = new WeatherTweetParser(twitterFile);
        wtp.mapJavaObject();

        tws = new Tweets();
        tweets = tws.getTweets();

        System.out.print(tweets.size());

        tweetIndex = 0;

        System.out.println("Parsing and inserting twitter file '" + twitterFile.getAbsolutePath() + "'...");

    //Step through all the tweets in each file, using the TweetParser class.
    while (true) {
        tweet = tweets.get(tweetIndex);
        user = tweet.new User();
        entity = tweet.new Entities();

        userMentions = entity.getUserMentions();
        hashtags = entity.getHashtags();

        if (tweet.getText() == null) {
            break;
        }
        numParsed++;

        Boolean success = wdbm.insertTweet(tweet, user);
        if (success == true) {
            numInserted++;
        }

        if (entity.getNumHashtags() > 0){

            for (int j = 0; j < entity.getNumHashtags(); j++) {
                wdbm.insertHashtag(tweet, hashtags.get(j)); 
            }   
        }

        if (entity.getNumUserMentions() > 0) {

            for (int k = 0; k < entity.getNumUserMentions(); k++) {
                wdbm.insertReference(tweet, userMentions.get(k));
            }
        }

        if (numParsed % UPDATE_INTERVAL == 0) {
            System.out.println(numParsed + " tweets parsed. " + numInserted + " tweets inserted into database...");
        }

        tweetIndex++;
    }

这是 JSON 文件的一部分。该文件由一系列推文组成，其中包含一些嵌套类，包括用户信息和实体信息(主题标签、用户提及)。这里我包含了数组的两个元素:

2014-01-03-11-03.terms.json

{
"tweets": [
    {
        "filter_level": "medium",
        "contributors": null,
        "text": "U know your ice fishing at home when ur snacks are sandwiches,chips,dips,beef jerky and all the goodies instead of just a case of beer #mom",
        "geo": null,
        "retweeted": false,
        "in_reply_to_screen_name": null,
        "truncated": false,
        "lang": "en",
        "entities": {
            "symbols": [

            ],
            "urls": [

            ],
            "hashtags": [
                {
                    "text": "mom",
                    "indices": [
                        135,
                        139
                    ]
                }
            ],
            "user_mentions": [

            ]
        },
        "in_reply_to_status_id_str": null,
        "id": 419137025376145408,
        "source": "<a href=\"http://twitter.com/download/iphone\" rel=\"nofollow\">Twitter for iPhone<\/a>",
        "in_reply_to_user_id_str": null,
        "favorited": false,
        "in_reply_to_status_id": null,
        "retweet_count": 0,
        "created_at": "Fri Jan 03 16:03:48 +0000 2014",
        "in_reply_to_user_id": null,
        "favorite_count": 0,
        "id_str": "419137025376145408",
        "place": null,
        "user": {
            "location": "",
            "default_profile": false,
            "profile_background_tile": true,
            "statuses_count": 5411,
            "lang": "en",
            "profile_link_color": "17EBCF",
            "profile_banner_url": "https://pbs.twimg.com/profile_banners/408240224/1384838946",
            "id": 408240224,
            "following": null,
            "protected": false,
            "favourites_count": 4222,
            "profile_text_color": "333333",
            "description": "It is what it is, no more, no less. Trust in the Lord. BSU Softball #5.  My whole being is happy - Psalm 16:9",
            "verified": false,
            "contributors_enabled": false,
            "profile_sidebar_border_color": "FFFFFF",
            "name": "Nicole Anne",
            "profile_background_color": "C0DEED",
            "created_at": "Wed Nov 09 05:03:58 +0000 2011",
            "default_profile_image": false,
            "followers_count": 452,
            "profile_image_url_https": "https://pbs.twimg.com/profile_images/413270299925164033/mWiJBKP2_normal.jpeg",
            "geo_enabled": true,
            "profile_background_image_url": "http://a0.twimg.com/profile_background_images/698793822/14d9ce538d96b435ad4449d5385a3ec1.jpeg",
            "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/698793822/14d9ce538d96b435ad4449d5385a3ec1.jpeg",
            "follow_request_sent": null,
            "url": null,
            "utc_offset": -32400,
            "time_zone": "Alaska",
            "notifications": null,
            "profile_use_background_image": true,
            "friends_count": 634,
            "profile_sidebar_fill_color": "DDEEF6",
            "screen_name": "NDupay",
            "id_str": "408240224",
            "profile_image_url": "http://pbs.twimg.com/profile_images/413270299925164033/mWiJBKP2_normal.jpeg",
            "listed_count": 1,
            "is_translator": false
        },
        "coordinates": null
    },
    {
        "filter_level": "medium",
        "contributors": null,
        "text": "Just watched DeBlasio shovel snow for the cameras and I have to say, his form is terrible. Looks a bit inexperienced.",
        "geo": null,
        "retweeted": false,
        "in_reply_to_screen_name": null,
        "truncated": false,
        "lang": "en",
        "entities": {
            "symbols": [

            ],
            "urls": [

            ],
            "hashtags": [

            ],
            "user_mentions": [

            ]
        },
        "in_reply_to_status_id_str": null,
        "id": 419137026458673152,
        "source": "<a href=\"http://twitter.com/download/iphone\" rel=\"nofollow\">Twitter for iPhone<\/a>",
        "in_reply_to_user_id_str": null,
        "favorited": false,
        "in_reply_to_status_id": null,
        "retweet_count": 0,
        "created_at": "Fri Jan 03 16:03:48 +0000 2014",
        "in_reply_to_user_id": null,
        "favorite_count": 0,
        "id_str": "419137026458673152",
        "place": null,
        "user": {
            "location": "",
            "default_profile": false,
            "profile_background_tile": false,
            "statuses_count": 2609,
            "lang": "en",
            "profile_link_color": "FF8000",
            "id": 163686045,
            "following": null,
            "protected": false,
            "favourites_count": 204,
            "profile_text_color": "333333",
            "description": "Love learning, Hockey #NYR, music and photography. My family is my whole life.",
            "verified": false,
            "contributors_enabled": false,
            "profile_sidebar_border_color": "EEEEEE",
            "name": "Steven Marques",
            "profile_background_color": "ACDED6",
            "created_at": "Wed Jul 07 01:26:25 +0000 2010",
            "default_profile_image": false,
            "followers_count": 56,
            "profile_image_url_https": "https://pbs.twimg.com/profile_images/378800000795958214/5e3ff928282ad692a36e941e5c5ff628_normal.jpeg",
            "geo_enabled": false,
            "profile_background_image_url": "http://abs.twimg.com/images/themes/theme18/bg.gif",
            "profile_background_image_url_https": "https://abs.twimg.com/images/themes/theme18/bg.gif",
            "follow_request_sent": null,
            "url": null,
            "utc_offset": -18000,
            "time_zone": "Eastern Time (US & Canada)",
            "notifications": null,
            "profile_use_background_image": true,
            "friends_count": 58,
            "profile_sidebar_fill_color": "F6F6F6",
            "screen_name": "SMGafanha",
            "id_str": "163686045",
            "profile_image_url": "http://pbs.twimg.com/profile_images/378800000795958214/5e3ff928282ad692a36e941e5c5ff628_normal.jpeg",
            "listed_count": 2,
            "is_translator": false
        },
        "coordinates": null
    },

这是 JSON 文件映射到的 Java 类，后面是映射 JSON 的类:

Tweets.java

public class Tweets {

private ArrayList<Tweet> tweets;

public Tweets() {
    tweets = new ArrayList<Tweet>();
}

public ArrayList<Tweet> getTweets() {
    return tweets;
}

public void setTweets(ArrayList<Tweet> tweets) {
    this.tweets = tweets;
}

public static class Tweet {

    private String text;
    @JsonProperty("source")
    private String postMethod;
    @JsonProperty("created_at")
    private String time;
    @JsonProperty("id")
    private String ID;

    public Tweet() {

    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public String getID() {
        return ID;
    }

    public void setID(String iD) {
        ID = iD;
    }

    public String getPostMethod() {
        return postMethod;
    }

    public void setPostMethod(String postMethod) {
        this.postMethod = postMethod;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public class User {

        private String location;
        @JsonProperty("screen_name")
        private String user;
        @JsonProperty("time_zone")
        private String timeZone;
        @JsonProperty("description")
        private String accountDescription;

        public User(){

        }

        public String getLocation() {
            return location;
        }

        public void setLocation(String location) {
            this.location = location;
        }

        public String getUser() {
            return user;
        }

        public void setUser(String user) {
            this.user = user;
        }

        public String getTimeZone() {
            return timeZone;
        }

        public void setTimeZone(String timeZone) {
            this.timeZone = timeZone;
        }

        public String getAccountDescription() {
            return accountDescription;
        }

        public void setAccountDescription(String accountDescription) {
            this.accountDescription = accountDescription;
        }
    }
    public class Entities {

        @JsonProperty("user_mentions")
        ArrayList<UserMention> userMentions;
        @JsonProperty("hashtags")
        ArrayList<Hashtag> hashtags;

        public Entities() {
            userMentions = new ArrayList<UserMention>();
            hashtags = new ArrayList<Hashtag>();                
        }

        public ArrayList<UserMention> getUserMentions() {
            return userMentions;
        }

        public int getNumUserMentions() {
            return userMentions.size();
        }

        public UserMention getUserMention(int index) {
            return userMentions.get(index);
        }

        public void setUserMentions(ArrayList<UserMention> userMentions) {
            this.userMentions = userMentions;
        }

        public ArrayList<Hashtag> getHashtags() {
            return hashtags;
        }

        public int getNumHashtags() {
            return hashtags.size();
        }

        public Hashtag getHashtag(int index) {
            return hashtags.get(index);
        }

        public void setHashtags(ArrayList<Hashtag> hashtags) {
            this.hashtags = hashtags;
        }

        public class UserMention {

            @JsonProperty("screen_name")
            private String userRef;

            public UserMention() {

            }

            public String getUserRef() {
                return userRef;
            }

            public void setUserRef(String userRef) {
                this.userRef = userRef;
            }
        }
        public class Hashtag {

            @JsonProperty("text")
            private String hashText;

            public Hashtag() {

            }

            public String getHashText() {
                return hashText;
            }

            public void setHashText(String hashText) {
                this.hashText = hashText;
            }
        }
    }
}


WeatherTweetParser.java

public class WeatherTweetParser {

private static File twitterFile;

public WeatherTweetParser(File twitterFile) {
    WeatherTweetParser.twitterFile = twitterFile;
}

public Tweets mapJavaObject() {

    Tweets ret = null;
    Path jsonFile = twitterFile.toPath();
    byte[] jsonData = null;

    try {
        jsonData = Files.readAllBytes(jsonFile);
    } catch (IOException e1) {
        e1.printStackTrace();
    }


    System.out.println("Mapping JSON to WeatherTweet Class.");

    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    try {
        ret = (Tweets) mapper.readValue(jsonData, Tweets.class);
    } catch (JsonParseException e) {
        e.printStackTrace();
    } catch (JsonMappingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    System.out.println("Finished Mapping of JSON File.");

    return ret;
}

public static void main(String[] args) {

    new WeatherTweetParser(twitterFile);
}   

这是控制台输出:

//Right before event passing the data to the method to enter into the db, 
//and right after each tweet is grabbed in WeatherDatabaseCreator.java    

username: null
location: null
time zone: null
account description: null

//Right Before inserting into database.

username: null
time/date: Jan 03 2014 11:03:48
text: RT @_PumpsAndJays: It's winter, right?
location: null
. . .
timezone = null

TL:DR:所以看起来我用来将 JSON 文件映射到的类没有存储用户和实体(我已经研究了后者，但它也不起作用，即所有空值)，但它存储推文信息(即时间、文本等)。问题是:为什么 WeatherTweetParser.java 映射的是 java 类的一部分而不是全部？

Answer 1

再一次，就像推文的情况一样，您没有将数据加载到“用户”对象。而不是:

user = tweet.new User();

您应该使用:

user = tweet.getUser();

您的 Tweet 类中还缺少以下内容:

@JsonProperty("user")
private User user;
public User getUser() { return user; }

我不知道您是如何生成 Tweets.java 文件的，但它似乎并不完整。考虑使用http://www.jsonschema2pojo.org/重新生成它。