Parsing dynamically generated JSON object names with Jackson

To answer the root cause of your exception, the @JsonAnySetter javadoc states

Marker annotation that can be used to define a non-static, two-argument method (first argument name of property, second value to set), [...]

As such, using a mixin like this

@JsonAnySettervoid setWikipediaPageMap(Map<String, WikipediaPage> wikipediaPageMap);

doesn't register it and therefore the property isn't found.

Honestly, don't use mixins if you control the data classes. You can directly map the fields as I've shown below.

I don't know how you are using your mixin, but the following works for me

String json = "{ \"query\": { \"pageids\": [ \"736\" ], \"pages\": { \"736\": { \"pageid\": 736, \"ns\": 0, \"title\": \"Albert Einstein\", \"contentmodel\": \"wikitext\", \"pagelanguage\": \"en\", \"touched\": \"2014-01-05T03:14:23Z\", \"lastrevid\": 588780054, \"counter\": \"\", \"length\": 106159 } } } }";ObjectMapper mapper = new ObjectMapper();JsonNode node =mapper.readTree(json);node = node.get("query").get("pages");Map<String, Page> pages = mapper.readValue(node.traverse(), new TypeReference<Map<String, Page>>() {});System.out.println(pages);

prints

{736=Page [pageid=736, ns=0, title=Albert Einstein, contentmodel=wikitext, pagelanguage=en, touched=2014-01-05T03:14:23Z, lastrevid=588780054, counter=, length=106159]}

Where Page is

class Page {    private int pageid;    private int ns;    private String title;    private String contentmodel;    private String pagelanguage;    private String touched; // this could be a Date, with the appropriate format configuration    private int lastrevid;    private String counter;    private int length;    @Override    public String toString() {        return "Page [pageid=" + pageid + ", ns=" + ns + ", title=" + title                + ", contentmodel=" + contentmodel + ", pagelanguage="                + pagelanguage + ", touched=" + touched + ", lastrevid="                + lastrevid + ", counter=" + counter + ", length=" + length                + "]";    }    public int getPageid() {        return pageid;    }    public void setPageid(int pageid) {        this.pageid = pageid;    }    public int getNs() {        return ns;    }    public void setNs(int ns) {        this.ns = ns;    }    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }    public String getContentmodel() {        return contentmodel;    }    public void setContentmodel(String contentmodel) {        this.contentmodel = contentmodel;    }    public String getPagelanguage() {        return pagelanguage;    }    public void setPagelanguage(String pagelanguage) {        this.pagelanguage = pagelanguage;    }    public String getTouched() {        return touched;    }    public void setTouched(String touched) {        this.touched = touched;    }    public int getLastrevid() {        return lastrevid;    }    public void setLastrevid(int lastrevid) {        this.lastrevid = lastrevid;    }    public String getCounter() {        return counter;    }    public void setCounter(String counter) {        this.counter = counter;    }    public int getLength() {        return length;    }    public void setLength(int length) {        this.length = length;    }}

All that is left is to put the Map<String, Page> as a field in some wrapper class for the query and pages JSON elements.