pátek 6. října 2017

REST Web Services with Jackson, Jersey and Payara Micro ... Level II

So ... I will continue with experiments started here and do some real work ... I continued to extend the API introduced in the recent blog, and I encountered some new problems ... for example I could not send a java.util.List in REST response with the same error as I already resolved in the request and also dates were only serialized (have you ever tried to serialize the GregorianCalendar instance?).
So i started to search on StackOverflow and found several solution - but neither one worked or at least it was not easy and nice. Then I started to think how it all works ... ;-)
Now I will stop talking, see the solution. I created new implementation of the web service to be more comprehensible what it does:

Jackson and Jersey

I am so dumb, do you know that? I mixed up these two names so long! So, what is the difference?
  • Jersey is the reference implementation of JAX-RS API. Nothing more to say. THE core. It's home is here. 
  • Jackson enhances the Jersey with much more stuff to be really usable. It's home is here. 
And this is a part of pom.xml of the web services war; versions are defined in some parent POM: 
    
    <!-- to use ResourceConfig class -->
    <dependency>
      <groupid>org.glassfish.jersey.core</groupid>
      <artifactid>jersey-server</artifactid>
    </dependency>
    <!-- to use JDK8 and other features, like java.time API or automatic ISO time formatting -->
    <dependency>
      <groupid>com.fasterxml.jackson.datatype</groupid>
      <artifactid>jackson-datatype-jdk8</artifactid>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupid>org.apache.logging.log4j</groupid>
      <artifactid>log4j-api</artifactid>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupid>org.apache.logging.log4j</groupid>
      <artifactid>log4j-core</artifactid>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupid>org.apache.commons</groupid>
      <artifactid>commons-lang3</artifactid>
      <scope>compile</scope>
    </dependency>

    <!-- to have better javadocs than in javaee-api -->
    <dependency>
      <groupid>javax.ws.rs</groupid>
      <artifactid>javax.ws.rs-api</artifactid>
      <scope>provided</scope>
    </dependency>    

    <!-- to have all Java EE 7 specifications in one dependency, but to have also the older javadoc -->
    <dependency>
      <groupid>javax</groupid>
      <artifactid>javaee-api</artifactid>
      <scope>provided</scope>
    </dependency>

ResouceConfig class

This class should be in root package of all your REST services - see calling of the method named packages in the constructor, that is the magic; it enables the annotation processing. And you know, there is more magic hidden in Maven dependencies not enabled by default. What I didn't know in first blog is that even Jackson is already in Glassfish/Payara (but not everything, see the dependencies again!). 

package org.dmatej.experiment.rest;

import javax.ws.rs.ApplicationPath;
import org.glassfish.jersey.server.ResourceConfig;
 

@ApplicationPath("") // use the application root
public class RestAppConfig extends ResourceConfig {
  public RestAppConfig() {
    packages(//
        RestAppConfig.class.getPackage().getName(), // search annotations in this class's package
        "com.fasterxml.jackson"// search in jackson's package
    );
  }
}

ContextResolver interface 

We enabled Jersey and Jackson, but that was not enough! Now we have to enable also the Jackson's extension modules. 

package org.dmatej.experiment.rest;

import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
 

@Provider
public class ObjectMapperContextResolver implements ContextResolver {

  private final ObjectMapper MAPPER;

  public ObjectMapperContextResolver() {
    MAPPER = new ObjectMapper();

// This did not find the Jdk8Module
    MAPPER.findAndRegisterModules();
    // enables ISO time parsing and formatting in REST communication.
    MAPPER.registerModule(new Jdk8Module());

    MAPPER.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
  }

  @Override
  public ObjectMapper getContext(Class type) {
    return MAPPER;
  }
}

And now the web service

Now it is pretty trivial and it will do what I expected. No unexplainable errors.

I think this blog entry is big enough and the implementation of Measurement transfer object is trivial, also MeasurementSaveResponse is trivial - it contains list of invalid records and some monitoring data.

The problem was the list - Jersey accepted list as a parameter but had thrown an exception if the list was in the response. Now I don't even need ArrayList in parameters and I can declare an abstract List. It also seems that those transfer objects don't need to have a complete set of getters and setters; Jersey uses reflection. 

package org.dmatej.experiment;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

import javax.ejb.EJB;
import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.GenericEntity;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

@Path("measurement")
public class MeasurementRestService {

  private static final Logger LOG = LogManager.getLogger(MeasurementRestService.class);

  // we are stateless, you know ...
  private List refusedMeasurements = new ArrayList<>();

  @POST
  @Path("save/{id1}/{id2}")
  @Consumes(MediaType.APPLICATION_JSON)
  @Produces(MediaType.APPLICATION_JSON)
  public Response save(//
      @PathParam("id1") final String id1, //
      @PathParam("id2") final String id2, //
      final List measurements) {

    final long start = System.currentTimeMillis();
    LOG.trace("save(id1={}, id2={}, measurements={})", id1, id2, measurements);

// invalid elements of the collection are moved to the refusedMeasurements collection.
    process(id1, id2, measurements);

    final MeasurementSaveResponse response = new MeasurementSaveResponse();
    response.setTimeInMillis(System.currentTimeMillis() - start);
    response.setRefusedMeasurements(this.refusedMeasurements);
    final Response restResponse = Response.ok(new GenericEntity<>(response, response.getClass())).build();
    return restResponse;
  }

Payara Micro and Uber jar 

No changes since the first blog. But we did not try it!

Call the web service! 


mvn clean install; mvn fish.payara.maven.plugins:payara-micro-maven-plugin:start -pl :experiment-uberjar

... and it will start: 

[2017-10-05T22:33:11.850+0200] [] [INFO] [] [javax.enterprise.system.core] [tid: _ThreadID=1 _ThreadName=main] [timeMillis: 1507235591850] [levelValue: 800] experiment-ws-0.0.1-SNAPSHOT was successfully deployed in 3 118 milliseconds.

[2017-10-05T22:33:11.851+0200] [] [INFO] [] [PayaraMicro] [tid: _ThreadID=1 _ThreadName=main] [timeMillis: 1507235591851] [levelValue: 800] Deployed 1 archive(s)

[2017-10-05T22:33:11.852+0200] [] [INFO] [] [PayaraMicro] [tid: _ThreadID=1 _ThreadName=main] [timeMillis: 1507235591852] [levelValue: 800] [[
 
Instance Configuration
Host: localhost
HTTP Port(s): 8080
HTTPS Port(s):
Instance Name: payara-micro
Instance Group: no-cluster
Deployed: experiment-ws-0.0.1-SNAPSHOT ( experiment-ws-0.0.1-SNAPSHOT war /experiment-ws-0.0.1-SNAPSHOT )

]]

[2017-10-05T22:33:11.865+0200] [] [INFO] [] [PayaraMicro] [tid: _ThreadID=1 _ThreadName=main] [timeMillis: 1507235591865] [levelValue: 800] [[
 
Payara Micro URLs
http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT

'experiment-ws-0.0.1-SNAPSHOT' REST Endpoints
POST    /experiment-ws-0.0.1-SNAPSHOT/measurement/save/{id1}/{id2}

]]

[2017-10-05T22:33:11.865+0200] [] [INFO] [] [PayaraMicro] [tid: _ThreadID=1 _ThreadName=main] [timeMillis: 1507235591865] [levelValue: 800] Payara Micro  4.1.2.173 #badassmicrofish (build 25) ready in 13 959 (ms)

Then open another console and run several curls: 

curl -H "Content-Type: application/json" -X OPTIONS -i http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/measurement/save/dm790321/xxx;
HTTP/1.1 200 OK
Server: Payara Micro #badassfish
Allow: POST,OPTIONS
Last-modified:  t, 05 X j 2017 11:18:02 CEST
Content-Type: application/vnd.sun.wadl+xml
Date: Thu, 05 Oct 2017 09:18:02 GMT
Content-Length: 715

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<application xmlns="http://wadl.dev.java.net/2009/02">
    <doc xmlns:jersey="http://jersey.java.net/" jersey:generatedBy="Jersey: 2.25.1 2017-01-19 16:23:50"/>
    <grammars/>
    <resources base="http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/">
        <resource path="measurement/save/dm790321/xxx">
            <method id="save" name="POST">
                <request>
                    <representation mediaType="application/json"/>
                </request>
                <response>
                    <representation mediaType="*/*"/>
                </response>
            </method>
        </resource>
    </resources>
</application>
Another example: 

curl -H "Content-Type: application/json" -X GET -i http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/application.wadl?detail=true
HTTP/1.1 200 OK
Server: Payara Micro #badassfish
Last-modified:  t, 05 X j 2017 15:59:02 CEST
Content-Type: application/vnd.sun.wadl+xml
Date: Thu, 05 Oct 2017 13:59:02 GMT
Content-Length: 5491

<application xmlns="http://wadl.dev.java.net/2009/02">
    <doc jersey:generatedby="Jersey: 2.25.1 2017-01-19 16:23:50" xmlns:jersey="http://jersey.java.net/">
    <doc jersey:hint="This is full WADL including extended resources. To get simplified WADL with users resources only do not use the query parameter detail. Link: http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/application.wadl" xmlns:jersey="http://jersey.java.net/">
    <grammars>
        <include href="application.wadl/xsd0.xsd">
            <doc title="Generated" xml:lang="en">
        </doc></include>
    </grammars>
    <resources base="http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/">
        <resource path="measurement">
            <resource path="save/{id1}/{id2}">
                <param name="id1" type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" />
                <param name="id2" type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" />
                <method id="save" name="POST">
                    <request>
                        <representation mediatype="application/json">
                    </representation></request>
                    <response>
                        <representation mediatype="application/json">
                    </representation></response>
                </method>
                <method id="apply" name="OPTIONS">
                    <request>
                        <representation mediatype="*/*">
                    </representation></request>
                    <response>
                        <representation mediatype="application/vnd.sun.wadl+xml">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
                <method id="apply" name="OPTIONS">
                    <request>
                        <representation mediatype="*/*">
                    </representation></request>
                    <response>
                        <representation mediatype="text/plain">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
                <method id="apply" name="OPTIONS">
                    <request>
                        <representation mediatype="*/*">
                    </representation></request>
                    <response>
                        <representation mediatype="*/*">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
            </resource>
        </resource>
        <resource path="application.wadl">
            <method id="getWadl" name="GET">
                <response>
                    <representation mediatype="application/vnd.sun.wadl+xml">
                    <representation mediatype="application/xml">
                </representation></representation></response>
                <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
            </method>
            <method id="apply" name="OPTIONS">
                <request>
                    <representation mediatype="*/*">
                </representation></request>
                <response>
                    <representation mediatype="text/plain">
                </representation></response>
                <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
            </method>
            <method id="apply" name="OPTIONS">
                <request>
                    <representation mediatype="*/*">
                </representation></request>
                <response>
                    <representation mediatype="*/*">
                </representation></response>
                <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
            </method>
            <resource path="{path}">
                <param name="path" type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" />
                <method id="getExternalGrammar" name="GET">
                    <response>
                        <representation mediatype="application/xml">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
                <method id="apply" name="OPTIONS">
                    <request>
                        <representation mediatype="*/*">
                    </representation></request>
                    <response>
                        <representation mediatype="text/plain">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
                <method id="apply" name="OPTIONS">
                    <request>
                        <representation mediatype="*/*">
                    </representation></request>
                    <response>
                        <representation mediatype="*/*">
                    </representation></response>
                    <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
                </method>
                <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
            </resource>
            <jersey:extended xmlns:jersey="http://jersey.java.net/">true</jersey:extended>
        </resource>
    </resources>
</doc></doc></application>
And finally, let's try timestamp and lists!: 

curl -H "Content-Type: application/json" -X POST -d '[{"timestamp":"2017-03-25T15:33:11.000+02:00", "channel":"15", "variable":"XXX", "value":"18"}, {"timestamp":"2017-03-25T15:33:11.000+02:00", "channel":"15", "variable":"XXX", "value":[null]}, {"timestamp":"2017-03-25T15:33:11.000+02:00", "channel":"15", "variable":[null], "value":"18"}]' -i http://localhost:8080/experiment-ws-0.0.1-SNAPSHOT/measurement/save/dm790321/fffff;
HTTP/1.1 200 OK
Server: Payara Micro #badassfish
Content-Type: application/json
Date: Thu, 05 Oct 2017 13:47:05 GMT
Content-Length: 132

{"countOfAccepted":2,"refusedMeasurements":[{"channel":15,"timestamp":"2017-03-25T15:33:11+02:00","value":18.0}],"timeInMillis":244}
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