test.proto

option java_package="test.protobuf";

message Foo {
    optional int32 foo = 1;
}

Wrapper.java

import com.fasterxml.jackson.annotation.JsonCreator;
import test.protobuf.Test;

public class Wrapper {
    public Test.Foo foo;

    @JsonCreator
    public Wrapper(Test.Foo foo) {
        this.foo = foo;
    }

    public Wrapper() {
        this(null);
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) return true;
        if ( !(other instanceof Wrapper)) return false;
        final Wrapper wrapper = (Wrapper) other;
        if (foo == null) return wrapper.foo == null;
        return wrapper.foo.equals(foo);
    }
}

wrapper.json

{
}

WrapperTest.java

import com.fasterxml.jackson.databind.ObjectMapper;
import com.hubspot.jackson.datatype.protobuf.ProtobufModule;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class WrapperTest {

    @Test
    public void wrapperFromJson() throws Exception {
        ObjectMapper mapper = new ObjectMapper().registerModule(new ProtobufModule());
        assertEquals(new Wrapper(), mapper.readValue(this.getClass().getResource("wrapper.json"), Wrapper.class));
    }
}