I have a hard time having a nice and clean way to implement this JsonParamInjectable. I searched on this forum and elsewhere but found nowhere an hint that would tell me how to implement it nice and clean.
For a jaxrs method :
public Object add(
@JsonParam("a") int a,
@JsonParam("b") int b
)
It parse a json {"a":1, "b":2} to param a and b
For this to work i implement an InjectableProvider, which create one JsonInjectable instance by method param.
@Provider
public class JsonParamProvider implements InjectableProvider<JsonParam, Type> {
private Gson gson;
public JsonParamProvider(@Context ServletConfig sc) throws Exception {
super();
this.gson = GsonFactory.newGson(sc);
}
@Override
public Injectable<Object> getInjectable(ComponentContext cc, JsonParam a, Type type) {
if (a.value() != null) {
String signature = cc.getAccesibleObject().toString();
return new JsonInjectable(signature, a, type, gson);
}
return null;
}
@Override
public ComponentScope getScope() {
return ComponentScope.Singleton;
}
The magic is done in this JsonInjectable, and its where id did a dirty trick :
public class JsonInjectable extends AbstractHttpContextInjectable<Object> {
private final JsonParam param;
private final Type type;
private final String signature;
private final Gson gson;
private static ThreadLocal<WeakReference<HttpContext>> contextCache = new ThreadLocal<WeakReference<HttpContext>>(){
@Override
protected WeakReference<HttpContext> initialValue() {
return new WeakReference<HttpContext>(null);
}
};
private static ThreadLocal<WeakReference<JsonElement>> entityCache = new ThreadLocal<WeakReference<JsonElement>>(){
@Override
protected WeakReference<JsonElement> initialValue() {
return new WeakReference<JsonElement>(null);
}
};
public JsonInjectable(String signature, JsonParam param, Type type, Gson gson) {
this.signature = signature;
this.param = param;
this.type = type;
this.gson = gson;
}
@Override
public Object getValue(HttpContext context) {
try {
JsonElement methodJsonElement = entityCache.get().get();
HttpContext context2 = contextCache.get().get();
if (context != context2) {
contextCache.set(new WeakReference<HttpContext>(context));
String entity = context.getRequest().getEntity(String.class);
System.out.println("entity:"+entity);
JsonParser parser = new JsonParser();
methodJsonElement = parser.parse(entity);
entityCache.set(new WeakReference<JsonElement>(methodJsonElement));
}
if (methodJsonElement == null || methodJsonElement.isJsonNull()) {
return null;
}
final JsonElement valueJsonElement = ((JsonObject)methodJsonElement).get(this.param.value());
if (valueJsonElement == null || valueJsonElement.isJsonNull()) {
return null;
}
if (this.type.equals(java.lang.Integer.class)) {
Number number = valueJsonElement.getAsNumber();
return number.intValue();
}
if (this.type.equals(java.lang.String.class)) {
return valueJsonElement.getAsString();
}
Class<?> c = ((Class<?>) this.type);
if (int.class.equals(c)) {
return valueJsonElement.getAsInt();
}
//other parsing code...
//try with gson
return this.gson.fromJson(valueJsonElement, this.type);
} catch (RuntimeException e) {
throw e;
}
}
The problem is, in some case entity is empty for, i suspect, a valid http request. Resulting in java.io.EOFException: End of input at line 1 column 2. This problem arise in production, but i am unable to reproduce it in testing env.
If there is a problem, it is surely related with "context != context2". For each injectable is binded to a param and injectables are called in an order i dont control, and each injectable work on the same data : parsed json from request entity. So to avoid re-parsing entity each time, i use context != context2 to detect if its a new request.
What is the nice and clean way to detect a new request so json parsing can only occur 1 time per request.
Ok this solution seem to work and is cleaner than the first one. Thanks for helping.
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
public abstract @interface JsonParam {
public abstract String value();
}
@Provider
public class JsonParamProvider implements InjectableProvider<JsonParam, Type> {
private Gson gson;
public JsonParamProvider(@Context ServletConfig sc) throws Exception {
super();
this.gson = GsonFactory.newGson(sc);
}
@Override
public Injectable<Object> getInjectable(ComponentContext cc, JsonParam a, Type type) {
if (a.value() != null) {
String signature = cc.getAccesibleObject().toString();
return new JsonParamInjectable(signature, a, type, gson);
}
return null;
}
@Override
public ComponentScope getScope() {
return ComponentScope.Singleton;
}
}
@Provider
public class JsonParamDispatchProvider extends AbstractResourceMethodDispatchProvider {
@Override
protected InjectableValuesProvider getInjectableValuesProvider(AbstractResourceMethod abstractResourceMethod) {
return new JsonParamInjectableValuesProvider(processParameters(abstractResourceMethod));
}
//copied from EntityParamDispatchProvider source code
private List<Injectable> processParameters(AbstractResourceMethod method) {
if ((null == method.getParameters()) || (0 == method.getParameters().size())) {
return Collections.emptyList();
}
boolean hasEntity = false;
final List<Injectable> is = new ArrayList<Injectable>(method.getParameters().size());
for (int i = 0; i < method.getParameters().size(); i++) {
final Parameter parameter = method.getParameters().get(i);
if (Parameter.Source.ENTITY == parameter.getSource()) {
hasEntity = true;
is.add(processEntityParameter(
parameter,
method.getMethod().getParameterAnnotations()[i]));
} else {
is.add(getInjectableProviderContext().
getInjectable(method.getMethod(), parameter, ComponentScope.PerRequest));
}
}
if (hasEntity)
return is;
// Try to find entity if there is one unresolved parameter and
// the annotations are unknown
if (Collections.frequency(is, null) == 1) {
final int i = is.lastIndexOf(null);
final Parameter parameter = method.getParameters().get(i);
if (Parameter.Source.UNKNOWN == parameter.getSource()) {
if (!parameter.isQualified()) {
final Injectable ij = processEntityParameter(
parameter,
method.getMethod().getParameterAnnotations()[i]);
is.set(i, ij);
}
}
}
return is;
}
//copied from EntityParamDispatchProvider source code
static final class EntityInjectable extends AbstractHttpContextInjectable<Object> {
final Class<?> c;
final Type t;
final Annotation[] as;
EntityInjectable(Class c, Type t, Annotation[] as) {
this.c = c;
this.t = t;
this.as = as;
}
@Override
public Object getValue(HttpContext context) {
return context.getRequest().getEntity(c, t, as);
}
}
//copied from EntityParamDispatchProvider source code
private Injectable processEntityParameter(
Parameter parameter,
Annotation[] annotations) {
return new EntityInjectable(parameter.getParameterClass(),
parameter.getParameterType(), annotations);
}
}
@SuppressWarnings("rawtypes")
public class JsonParamInjectableValuesProvider extends InjectableValuesProvider {
public static final String JSON_ELEMENT_CONTEXT_PROPERTY_KEY = "JsonParamInjectableValuesProvider.jsonElementContextPropertyKey";
public JsonParamInjectableValuesProvider(List<Injectable> is) {
super(is);
}
/**
* Get the injectable values.
*
* @param context the http contest.
* @return the injectable values. Each element in the object array
* is a value obtained from the injectable at the list index
* that is the element index.
*/
@Override
public Object[] getInjectableValues(HttpContext context) {
List<AbstractHttpContextInjectable> is = getInjectables();
final Object[] params = new Object[is.size()];
try {
//parse json element and add it to context
context.getProperties().put(JSON_ELEMENT_CONTEXT_PROPERTY_KEY, parseJsonElement(context));
//map jsonElement with injectable
int index = 0;
for (AbstractHttpContextInjectable i : is) {
params[index++] = i.getValue(context);
}
return params;
} catch (WebApplicationException e) {
throw e;
} catch (ContainerException e) {
throw e;
} catch (RuntimeException e) {
throw new ContainerException("Exception obtaining parameters", e);
} finally {
context.getProperties().remove(JSON_ELEMENT_CONTEXT_PROPERTY_KEY);
}
}
private static JsonElement parseJsonElement(HttpContext context) {
String entity = context.getRequest().getEntity(String.class);
if (StringUtils.isBlank(entity)) {
throw new ContainerException("entity is blank for request " + context.getRequest());
}
JsonParser parser = new JsonParser();
return parser.parse(entity);
}
}
public class JsonParamInjectable extends AbstractHttpContextInjectable<Object> {
private final JsonParam param;
private final Type type;
private final String signature;
private final Gson gson;
public JsonParamInjectable(String signature, JsonParam param, Type type, Gson gson) {
this.signature = signature;
this.param = param;
this.type = type;
this.gson = gson;
}
@Override
public Object getValue(HttpContext context) {
try {
JsonElement jsonElement = (JsonElement) context.getProperties().get(JsonParamInjectableValuesProvider.JSON_ELEMENT_CONTEXT_PROPERTY_KEY);
if (jsonElement == null) {
throw new ContainerException("invalid json element in context. " + context.getRequest());
}
if (jsonElement == null || jsonElement.isJsonNull()) {
return null;
}
final JsonElement valueJsonElement = ((JsonObject)jsonElement).get(this.param.value());
if (valueJsonElement == null || valueJsonElement.isJsonNull()) {
return null;
}
if (this.type.equals(java.lang.Integer.class)) {
Number number = valueJsonElement.getAsNumber();
return number.intValue();
}
if (this.type.equals(java.lang.String.class)) {
return valueJsonElement.getAsString();
}
Class<?> c = ((Class<?>) this.type);
if (int.class.equals(c)) {
return valueJsonElement.getAsInt();
}
if (long.class.equals(c)) {
return valueJsonElement.getAsLong();
}
if (boolean.class.equals(c)) {
return valueJsonElement.getAsBoolean();
}
//other parsing code...
//try with gson
return this.gson.fromJson(valueJsonElement, this.type);
} catch (RuntimeException e) {
throw e;
}
}
@Override
public String toString() {
return "JsonParamInjectable " + this.hashCode() + " [param=" + this.param + ", type=" + this.type + ", signature=" + this.signature + "]"; }
}