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How would I parse this JSON, looks like an array but no “[]”s

由 ￡可爱￡侵袭症＋ 提交于 2019-12-12 02:19:02

问题


I'm using Springboot with RestTemplate to parse JSON. All the resources i'm looking at deal with arrays, but I understand that arrays need brackets ([]).

I have JSON here (https://rsbuddy.com/exchange/summary.json)

(short example in case link goes down)

    {"2": {"overall_average": 216, "sp": 5, "members": true, "buy_average": 215,
 "sell_average": 215, "name": "Cannonball", "id": 2}, "6": {"overall_average":
 173518, "sp": 187500, "members": true, "buy_average": 190176, "sell_average": 
189343, "name": "Cannon base", "id": 6}, ... , 

"12287": {"overall_average": 0,
     "sp": 5200, "members": false, "buy_average": 3234, "sell_average": 3234, 
    "name": "Mithril platebody (t)", "id": 12287}}

that feels like it should be an array because it's a list, but it doesn't have brackets, and can't be parsed with the following code:

public List<ItemSummaryContainer> consumeItems() {

        ResponseEntity<List<ItemSummaryContainer>> itemSummaryResponse =
                restTemplate.exchange(url, HttpMethod.GET, null, new ParameterizedTypeReference<List<ItemSummaryContainer>>() {

                });

        return itemSummaryResponse.getBody();
    }

ItemSummaryContainer class

@JsonIgnoreProperties(ignoreUnknown = true)
public class ItemSummaryContainer {

    private int id;
    private ItemSummary itemSummary;


    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public ItemSummary getItemSummary() {
        return itemSummary;
    }
    public void setItemSummary(ItemSummary itemSummary) {
        this.itemSummary = itemSummary;
    }   
}

ItemSummary class

@JsonIgnoreProperties(ignoreUnknown = true)
public class ItemSummary {

    private Integer id;
    private String name;
    private Integer members;

    public ItemSummary() {

    }
    public ItemSummary(Integer id, String name, Integer members) {
        super();
        this.id = id;
        this.name = name;
        this.members = members;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getMembers() {
        return members;
    }
    public void setMembers(int members) {
        this.members = members;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        ItemSummary other = (ItemSummary) obj;
        if (id != other.id)
            return false;
        if (members != other.members)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }   
}

Stacktrace

java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:801) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:782) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:769) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1185) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1174) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    at com.tjwhalen.game.Application.main(Application.java:50) [classes/:na]
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: java.io.PushbackInputStream@55f8669d; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: java.io.PushbackInputStream@55f8669d; line: 1, column: 1]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:228) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:213) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:95) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:884) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:868) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:622) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:580) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:526) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at com.tjwhalen.game.service.dao.ItemSummaryURLConsumer.consumeItems(ItemSummaryURLConsumer.java:25) ~[classes/:na]
    at com.tjwhalen.game.service.impl.ItemSummaryRestServiceImpl.getItems(ItemSummaryRestServiceImpl.java:25) ~[classes/:na]
    at com.tjwhalen.game.loader.LoadItems.load(LoadItems.java:38) ~[classes/:na]
    at com.tjwhalen.game.loader.LoaderRunner.execute(LoaderRunner.java:26) ~[classes/:na]
    at com.tjwhalen.game.Application$AppConfig.run(Application.java:78) ~[classes/:na]
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:798) [spring-boot-1.4.0.RELEASE.jar:1.4.0.RELEASE]
    ... 6 common frames omitted
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: java.io.PushbackInputStream@55f8669d; line: 1, column: 1]
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:261) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.DeserializationContext.reportMappingException(DeserializationContext.java:1233) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1121) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1074) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:328) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:259) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789) ~[jackson-databind-2.8.1.jar:2.8.1]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2913) ~[jackson-databind-2.8.1.jar:2.8.1]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:225) ~[spring-web-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    ... 19 common frames omitted

Please advise, or ask any needed clarifying questions,

Thanks


回答1:


The JSON you are trying to parse is perfectly valid. It's not an array, but it's still valid:

{
  "2": {
    "overall_average": 211,
    "buy_average": 208,
    "members": true,
    "id": 2,
    "name": "Cannonball",
    "sell_average": 210,
    "sp": 5
  },
  "6": {
    "overall_average": 0,
    "buy_average": 0,
    "members": true,
    "id": 6,
    "name": "Cannon base",
    "sell_average": 0,
    "sp": 187500
  },
  "12289": {
    "overall_average": 9999,
    "buy_average": 0,
    "members": false,
    "id": 12289,
    "name": "Mithril platelegs (t)",
    "sell_average": 9999,
    "sp": 2600
  },
  ...
}

The ItemSummary class could be defined as following:

@JsonIgnoreProperties(ignoreUnknown = true)
public class ItemSummary {

    private String id;
    private String name;
    private boolean members;

    // Getters and setters omitted
}

And the whole JSON could be parsed into a Map<String, ItemSummary>. See the details below.

Parsing the JSON into a Map<String, ItemSummary>

With Spring REST Template, use:

RestTemplate restTemplate = new RestTemplate(); 
ResponseEntity<Map<String, ItemSummary>> response = 
        restTemplate.exchange(
            "https://rsbuddy.com/exchange/summary.json", 
            HttpMethod.GET, 
            null, 
            new ParameterizedTypeReference<Map<String, ItemSummary>>() {});

Map<String, ItemSummary> map = response.getBody();

With Jackson's ObjectMapper, you could have:

ObjectMapper mapper = new ObjectMapper();
Map<String, ItemSummary> map = 
    mapper.readValue(new URL("https://rsbuddy.com/exchange/summary.json"),
                     new TypeReference<Map<String, ItemSummary>>() {});

Wrapping the Map<String, ItemSummary> into a class

If you need a wrapper class around the Map<String, ItemSummary>, define it as following:

@JsonIgnoreProperties(ignoreUnknown = true)
public class ItemSummaryContainer {

    private Map<String, ItemSummary> items;

    @JsonCreator
    public ItemSummaryContainer(Map<String, ItemSummary> items) {
        this.items = items;
    }

    // Getters and setters omitted
}

With Spring REST Template, use:

RestTemplate restTemplate = new RestTemplate(); 
ResponseEntity<ItemSummaryContainer> response = 
    restTemplate.exchange(
        "https://rsbuddy.com/exchange/summary.json", 
        HttpMethod.GET, 
        null, 
        new ParameterizedTypeReference<ItemSummaryContainer>() {});

ItemSummaryContainer container = response.getBody();

And with Jackson's ObjectMapper, you would have:

ObjectMapper mapper = new ObjectMapper();
ItemSummaryContainer container = 
    mapper.readValue(new URL("https://rsbuddy.com/exchange/summary.json"),
                     ItemSummaryContainer.class);



回答2:


It's mismatch between JSON and the JAVA class.

Which is in your scope ? JSON or Java ? Fix either of these and according to Json change Java class or vice versa.

Your JSON:

{
"2" : {
    "members" : true,
    "sell_average" : 207,
    "id" : 2,
    "buy_average" : 206,
    "sp" : 5,
    "name" : "Cannonball",
    "overall_average" : 209
},
"6" : {
    "members
.....

As per this it is expecting a Java object as in your description and not LIST.

When you cannot change JSON input, match your java class to be 

@JsonIgnoreProperties(ignoreUnknown = true)
public class ItemSummaryContainer {

    private Map<Integer,  ItemSummary> items;
    // getter and setter
}

If it is other side, change your JSON.



来源：https://stackoverflow.com/questions/39462204/how-would-i-parse-this-json-looks-like-an-array-but-no-s

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json
Spring
jackson
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