我试图使用GSON将7000 POJO的阵列序列化,而序列化时间极为缓慢。

public class Case {
    private Long caseId;
    private Key<Organization> orgKey;

    private Key<Workflow> workflowKey;
    private Key<User> creatorKey;

    private Date creationTimestamp;
    private Date lastUpdatedTimestamp;

    private String name;
    private String stage;
    private String notes;
}

关键字段使用自定义的序列器/取消序列器进行序列化:

public class GsonKeySerializerDeserializer implements JsonSerializer<Key<?>>, JsonDeserializer<Key<?>>{

@Override
public JsonElement serialize(Key<?> src, Type typeOfSrc, JsonSerializationContext arg2) {
    return new JsonPrimitive(src.getString());
}

@Override
public Key<?> deserialize(JsonElement src, Type typeOfSrc, JsonDeserializationContext arg2) throws JsonParseException {
    if (src.isJsonNull() || src.getAsString().isEmpty()) {
        return null;
    }

    String s = src.getAsString();
    com.google.appengine.api.datastore.Key k = KeyFactory.stringToKey(s);
    return new Key(k);
}
}

为了对照手写JSON序列器测试性能,我测试了以下代码,它可以比GSON大约快10x的同一组Case天体序列。

List<Case> cases = (List<Case>) retVal;
JSONArray a = new JSONArray();
for (Case c : cases) {
    JSONObject o = new JSONObject();
    o.put("caseId", c.getCaseId());
    o.put("orgKey", c.getOrgKey().getString());
    o.put("workflowKey", c.getWorkflowKey().getString());
    o.put("creatorKey", c.getCreatorKey().getString());
    o.put("creationTimestamp", c.getCreationTimestamp().getTime());
    o.put("lastUpdatedTimestamp", c.getLastUpdatedTimestamp().getTime());
    o.put("name", c.getName());
    o.put("stage", c.getStage());
    o.put("notes", c.getNotes());
    a.put(o);

}
String json = a.toString();

知道Gsonson为什么在这个案子里表现这么差吗?

<强> UPDATE

这里的代码是开始序列的代码 :

Object retVal = someFunctionThatReturnsAList();
String json = g.toJson(retVal);
resp.getWriter().print(json);

<强>UPDATE2

以下是一个非常简单的测试案例, 说明与org.json相比表现不佳:

List<Foo> list = new ArrayList<Foo>();
for (int i = 0; i < 7001; i++) {
    Foo f = new Foo();
    f.id = new Long(i);
    list.add(f);
}

Gson gs = new Gson();
long start = System.currentTimeMillis();
String s = gs.toJson(list);
System.out.println("Serialization time using Gson: " + ((double) (System.currentTimeMillis() - start) / 1000));


start = System.currentTimeMillis();
JSONArray a = new JSONArray();
for (Foo f : list) {
    JSONObject o = new JSONObject();
    o.put("id", f.id);
    a.put(o);

}
String json = a.toString();
System.out.println("Serialization time using org.json: " + ((double) (System.currentTimeMillis() - start) / 1000));

System.out.println(json.equals(s));

富尔在哪里:

public class Foo {
public Long id;
}

这一产出:

Serialization time using Gson: 0.233
Serialization time using org.json: 0.028
true

近10x的性能差异!