FunctionClient

The @FunctionClient annotation makes it very straightforward to invoke local or remotely deployed functions. For example, given the following function:

Max Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws;
import io.micronaut.function.FunctionBean;
import java.util.function.Supplier;
@FunctionBean("max")
public class MaxFunction implements Supplier<Integer> {
    private final MathService mathService;
    public MaxFunction(MathService mathService) {
        this.mathService = mathService;
    }
    @Override
    public Integer get() {
        return mathService.max();
    }
}

Max Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws
import groovy.transform.Field
math.multiplier = 2
@Field MathService mathService
Long max() {
    mathService.max()
}

Max Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws
import io.micronaut.function.FunctionBean
import java.util.function.Supplier
@FunctionBean("max")
class MaxFunction(private val mathService: MathService) : Supplier<Int> {
    override fun get(): Int {
        return mathService.max()
    }
}

The following client can be used to execute it.

Using @FunctionClient to Discover Function

import io.micronaut.runtime.server.EmbeddedServer;
import io.micronaut.function.client.FunctionClient;
import org.junit.Test;
import javax.inject.Named;
import static org.junit.Assert.assertEquals;
    @FunctionClient
    interface MathClient {
        Long max(); (1)
    }

Using @FunctionClient to Discover Function

import io.micronaut.function.client.FunctionClient
import javax.inject.Named
    @FunctionClient
    static interface MathClient {
        Long max() (1)
    }

Using @FunctionClient to Discover Function

import io.kotlintest.shouldBe
import io.kotlintest.specs.StringSpec
import io.micronaut.context.ApplicationContext
import io.micronaut.runtime.server.EmbeddedServer
import io.micronaut.function.client.FunctionClient
import io.micronaut.http.client.RxHttpClient
import javax.inject.Named
    @FunctionClient
    internal interface MathClient {
        fun max(): Long?  (1)
    }

If you would like the names of the client interface and target function to be different, you can use the Named annotation to specify the target method name.

Round Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws;
import io.micronaut.function.FunctionBean;
import java.util.function.Function;
@FunctionBean("round")
public class RoundFunction implements Function<Float, Integer> {
    private final MathService mathService;
    public RoundFunction(MathService mathService) {
        this.mathService = mathService;
    }
    @Override
    public Integer apply(Float aFloat) {
        return mathService.round(aFloat);
    }
}

Round Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws
import groovy.transform.Field
math.multiplier = 2
@Field MathService mathService
int round(float value) {
    mathService.round(value)
}

Round Function

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.micronaut.docs.function.client.aws
import io.micronaut.function.FunctionBean
import java.util.function.Function
@FunctionBean("round")
class RoundFunction(private val mathService: MathService) : Function<Float, Int> {
    override fun apply(aFloat: Float): Int {
        return mathService.round(aFloat)
    }
}

The named annotation can be placed on the client as well.

Using @Named to customize target method

import io.micronaut.runtime.server.EmbeddedServer;
import io.micronaut.function.client.FunctionClient;
import org.junit.Test;
import javax.inject.Named;
import static org.junit.Assert.assertEquals;
    @FunctionClient
    interface MathClient {
        @Named("round")
        int rnd(float value);
    }

Using @Named to customize target method

import io.micronaut.function.client.FunctionClient
import javax.inject.Named
    @FunctionClient
    static interface MathClient {
        @Named("round")
        int rnd(float value)
    }

Using @Named to customize target method

import io.kotlintest.shouldBe
import io.kotlintest.specs.StringSpec
import io.micronaut.context.ApplicationContext
import io.micronaut.runtime.server.EmbeddedServer
import io.micronaut.function.client.FunctionClient
import io.micronaut.http.client.RxHttpClient
import javax.inject.Named
    @FunctionClient
    internal interface MathClient {
        @Named("round")
        fun rnd(value: Float): Int
    }

Functions that only return a value are mapped to HTTP GET requests, whilst functions that accept an input require an HTTP POST.

For a example, given the following function:

import io.micronaut.function.FunctionBean;
import java.util.function.Function;
@FunctionBean("isbn-validator")
public class IsbnValidatorFunction implements Function<IsbnValidationRequest, IsbnValidationResponse> {
    @Override
    public IsbnValidationResponse apply(IsbnValidationRequest request) {
        return new IsbnValidationResponse();
    }
}

import io.micronaut.function.FunctionBean
import java.util.function.Function
@FunctionBean("isbn-validator")
class IsbnValidatorFunction implements Function<IsbnValidationRequest, IsbnValidationResponse> {
    @Override
    IsbnValidationResponse apply(IsbnValidationRequest request) {
        return new IsbnValidationResponse()
    }
}

import io.micronaut.function.FunctionBean
import java.util.function.Function
@FunctionBean("isbn-validator")
class IsbnValidatorFunction : Function<IsbnValidationRequest, IsbnValidationResponse> {
    override fun apply(request: IsbnValidationRequest): IsbnValidationResponse {
        return IsbnValidationResponse()
    }
}

The function can be accessed using the IsbnValidatorClient interface listed below.

import io.micronaut.function.client.FunctionClient;
import io.micronaut.http.annotation.Body;
import io.reactivex.Single;
import javax.inject.Named;
@FunctionClient
public interface IsbnValidatorClient {
    @Named("isbn-validator")
    Single<IsbnValidationResponse> validate(@Body IsbnValidationRequest request); (1)
}

import io.micronaut.function.client.FunctionClient;
import io.micronaut.http.annotation.Body;
import io.reactivex.Single;
import javax.inject.Named;
@FunctionClient
interface IsbnValidatorClient {
    @Named("isbn-validator")
    Single<IsbnValidationResponse> validate(@Body IsbnValidationRequest request) (1)
}

import io.micronaut.function.client.FunctionClient
import io.micronaut.http.annotation.Body
import io.reactivex.Single
import javax.inject.Named
@FunctionClient
interface IsbnValidatorClient {
    @Named("isbn-validator")
    fun validate(@Body request: IsbnValidationRequest): Single<IsbnValidationResponse>  (1)
}