@FormParam and Optional<T>

[Olve Hansen]

Just noticed that Optional<T> doesn't work with @FormParam.

https://github.com/dropwizard/dropwizard/issues/669

Any suggestions for simple solutions? I'll also try to make time for a PR in the not too distant future...

Regards, 

Olve

[Kris Massey]

Hi Olve,

I've worked around this problem as below. All of the code is within the Dropwizard/Jersey source code, I just lifted the bits I needed.

Essentially copy the OptionalQueryParamInjectableProvider.class and create on for the @FormParam annotaiton 

import com.google.common.base.Optional;

import com.sun.jersey.api.ParamException;

import com.sun.jersey.api.core.HttpContext;

import com.sun.jersey.api.core.HttpRequestContext;

import com.sun.jersey.api.model.Parameter;

import com.sun.jersey.api.representation.Form;

import com.sun.jersey.core.header.MediaTypes;

import com.sun.jersey.core.spi.component.ComponentContext;

import com.sun.jersey.core.spi.component.ComponentScope;

import com.sun.jersey.core.spi.component.ProviderServices;

import com.sun.jersey.server.impl.inject.AbstractHttpContextInjectable;

import com.sun.jersey.server.impl.model.method.dispatch.FormDispatchProvider;

import com.sun.jersey.server.impl.model.parameter.multivalued.ExtractorContainerException;

import com.sun.jersey.server.impl.model.parameter.multivalued.MultivaluedParameterExtractor;

import com.sun.jersey.server.impl.model.parameter.multivalued.MultivaluedParameterExtractorFactory;

import com.sun.jersey.server.impl.model.parameter.multivalued.StringReaderFactory;

import com.sun.jersey.spi.inject.Injectable;

import com.sun.jersey.spi.inject.InjectableProvider;

import javax.ws.rs.FormParam;

import javax.ws.rs.core.Context;

import javax.ws.rs.core.MediaType;

import javax.ws.rs.core.MultivaluedMap;

import javax.ws.rs.ext.Provider;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

/**

 * User: kris massey

 */

@Provider

public class OptionalFormParamInjectableProvider implements InjectableProvider<FormParam, Parameter> {

    private static class FormParamInjectable extends AbstractHttpContextInjectable<Object> {

        private final MultivaluedParameterExtractor extractor;

        private final boolean decode;

        private FormParamInjectable(MultivaluedParameterExtractor extractor,

                                     boolean decode) {

            this.extractor = extractor;

            this.decode = decode;

        }

        @Override

        public Object getValue(HttpContext context) {

            Form form = getCachedForm(context);

            if (form == null) {

                form = getForm(context);

                cacheForm(context, form);

            }

            try {

                return  Optional.fromNullable(extractor.extract(form));

            } catch (ExtractorContainerException e) {

                throw new ParamException.FormParamException(e.getCause(),

                        extractor.getName(), extractor.getDefaultStringValue());

            }

        }

        private void cacheForm(final HttpContext context, final Form form) {

            context.getProperties().put(FormDispatchProvider.FORM_PROPERTY, form);

        }

        private Form getCachedForm(final HttpContext context) {

            return (Form) context.getProperties().get(FormDispatchProvider.FORM_PROPERTY);

        }

        private HttpRequestContext ensureValidRequest(final HttpRequestContext r) throws IllegalStateException {

            if (r.getMethod().equals("GET")) {

                throw new IllegalStateException(

                        "The @FormParam is utilized when the request method is GET");

            }

            if (!MediaTypes.typeEquals(MediaType.APPLICATION_FORM_URLENCODED_TYPE, r.getMediaType())) {

                throw new IllegalStateException(

                        "The @FormParam is utilized when the content type of the request entity "

                                + "is not application/x-www-form-urlencoded");

            }

            return r;

        }

        private Form getForm(HttpContext context) {

            final HttpRequestContext r = ensureValidRequest(context.getRequest());

            return r.getFormParameters();

        }

    }

    private static class OptionalExtractor implements MultivaluedParameterExtractor {

        private final MultivaluedParameterExtractor extractor;

        private OptionalExtractor(MultivaluedParameterExtractor extractor) {

            this.extractor = extractor;

        }

        @Override

        public String getName() {

            return extractor.getName();

        }

        @Override

        public String getDefaultStringValue() {

            return extractor.getDefaultStringValue();

        }

        @Override

        public Object extract(MultivaluedMap<String, String> parameters) {

            return Optional.fromNullable(extractor.extract(parameters));

        }

    }

    private final ProviderServices services;

    private MultivaluedParameterExtractorFactory factory;

    public OptionalFormParamInjectableProvider(@Context ProviderServices services) {

        this.services = services;

    }

    @Override

    public ComponentScope getScope() {

        return ComponentScope.PerRequest;

    }

    @Override

    public Injectable<?> getInjectable(ComponentContext ic,

                                       FormParam a,

                                       Parameter c) {

        if (isExtractable(c)) {

            final OptionalExtractor extractor = new OptionalExtractor(getFactory().get(unpack(c)));

            return new FormParamInjectable(extractor, !c.isEncoded());

        }

        return null;

    }

    private boolean isExtractable(Parameter param) {

        return (param.getSourceName() != null) && !param.getSourceName().isEmpty() &&

                param.getParameterClass().isAssignableFrom(Optional.class) &&

                (param.getParameterType() instanceof ParameterizedType);

    }

    private Parameter unpack(Parameter param) {

        final Type typeParameter = ((ParameterizedType) param.getParameterType()).getActualTypeArguments()[0];

        return new Parameter(param.getAnnotations(),

                param.getAnnotation(),

                param.getSource(),

                param.getSourceName(),

                typeParameter,

                (Class<?>) typeParameter,

                param.isEncoded(),

                param.getDefaultValue());

    }

    private MultivaluedParameterExtractorFactory getFactory() {

        if (factory == null) {

            final StringReaderFactory stringReaderFactory = new StringReaderFactory();

            stringReaderFactory.init(services);

            this.factory = new MultivaluedParameterExtractorFactory(stringReaderFactory);

        }

        return factory;

    }

}

 

Then you need to register it with the Jersey Environment in you Application configuration as below:

environment.jersey().getResourceConfig().getClasses().add(OptionalFormParamInjectableProvider.class);

Does the trick for my needs, hopefully someone might find it helpful!

[Olve Hansen]

I'll test that - looks good. Basically a copy of the QueryParam in dw? This could go into a PR more or less unchanged I guess..

Thanks!

Olve

[Kris Massey]

Almost a copy. It's partly from the QueryParam and partly from somewhere else (can't remember exactly where! More than likely the FormParamInjectable)

Before creating a PR I'd want to do some refactoring to split the common code into external classes. Hopefully I'll get a chance to do it later this week.

Sent from my iPhone

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[Kris Massey]

PR request crated -> https://github.com/dropwizard/dropwizard/pull/677