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intent

produce a docker image with 3 main layers:

• OS / java - rarely changes, good caching and sharing among apps in a kubernetes cluster
• dependencies - changes are not too frequent, good caching among app versions
• app jar - changes with every version, but should be quite compact

how to

in build.gradle.kts:

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package mailhog


/*
dependencies:
    testImplementation("org.testcontainers:testcontainers:1.15.2")
    testImplementation(platform("org.http4k:http4k-bom:4.3.5.4"))
    testImplementation("org.http4k:http4k-core")
    testImplementation("org.http4k:http4k-client-apache") {
        because("mailhog http api messages access")

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public class SafeCachingFactorizer implements Servlet {
    private static class FactorResult { BigInteger number; BigInteger[] factors; }

    private volatile FactorResult lastResult = null;

    public void service(ServletRequest req, ServletResponse resp) {
        BigInteger i = extractFromRequest(req);
        FactorResult result = this.lastResult;
        if (result == null || !i.equals(result.number)) {
            result = new FactorResult() { { number = i; factors = factor(i); } };

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import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonMappingException;

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import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import de.undercouch.bson4jackson.BsonGenerator;
import de.undercouch.bson4jackson.serializers.BsonSerializer;

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package restx.spring;

import org.springframework.web.context.ContextLoaderListener;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContextEvent;

/**
 * User: xavierhanin

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@Module(priority = -100)
public class JongoModule {

    JacksonMapper.Builder getJacksonMapperBuilder() {
        return new JacksonMapper.Builder()
                .registerModule(new BsonJodaTimeModule())
                .withView(Views.Private.class)
                ;
    }

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// In AppModule class, or could be in a dedicated module.


    @Provides
    public DBI dbi(@Named("datasource") DataSource ds) {
        return new DBI(ds);
    }

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A few notes on java annotation processing, collected when working on RESTX annotation processor.

Don't register multiple annotation processor on same annotation.

It fails silently.

Disable annotation processing in module defining an annotation processor.

Use -proc:none javac option. In restx build you can use this fragment: classpath:///restx/build/fragments/maven/annotation-processing-disable.xml

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    @GET("/helloConcat")
    @PermitAll
    public Iterable<String> concatMessages(String q) {
        String c = q + "test";
        return asList(NAMES)
                .stream()
                .map((s) -> (s + c))
                .collect(Collectors.toList());
    }