MAVEN Web Application with Jetty

MAVEN Web Application with Jetty

Recently, I need to create Java Project which support servlet and running under jetty, so here is the steps.

Create the project
>mvn archetype:generate -DgroupId=com.j2c -DartifactId=healthcheckcontainer -DarchetypeArtifactId=maven-archetype-webapp -DinteractiveMode=false

After it created, I will get the pom.xml similar to following
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.sillycat.solr</groupId>
    <packaging>war</packaging>
    <version>1.0</version>
    <name>solr-healthcheck</name>
    <url>http://maven.apache.org</url>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <version>9.4.7.v20170914</version>
                <configuration>
                    <scanIntervalSeconds>10</scanIntervalSeconds>
                    <webApp>
                        <contextPath>/healthcheck</contextPath>
                        <webInfIncludeJarPattern>.*/spring-[^/]*\.jar$</webInfIncludeJarPattern>
                    </webApp>
                </configuration>
            </plugin>
        </plugins>
        <finalName>solr-healthcheck</finalName>
    </build>
    <artifactId>solr-healthcheck</artifactId>
</project>

It is a very simple servlet things to support parse and monitor a JSON response, web.xml is as follow:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
    <display-name>SOLR HealthCheck</display-name>
    <servlet>
        <servlet-name>healthCheckServlet</servlet-name>
        <servlet-class>com.sillycat.solr.HealthCheckServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>healthCheckServlet</servlet-name>
        <url-pattern>/healthcheck</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>healthCheckServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

The servlet class will be as simple as follow HealthCheckServlet.java
package com.sillycat.solr;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HealthCheckServlet extends HttpServlet {

    private static final long serialVersionUID = -5366378871837937127L;

    private final static Logger logger = LoggerFactory.getLogger(HealthCheckServlet.class);

    private String host = "localhost";
    private String collection = "allJobs";
    private String shard = "shard1";

    public void init() throws ServletException {
        super.init();
        host = System.getProperty("host");
        collection = System.getProperty("collection");
        shard = System.getProperty("shard");
    }

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        final String replicaState = ReplicaState.getReplicaState(host, collection, shard);
        if (!ReplicaState.isReplicaActive(replicaState)) {
            final String message = "Replica is NOT active(host=" + host + ", collection=" + collection + ", shard="
                    + shard + ", state=" + replicaState + ")";
            logger.info(message);

            resp.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
            resp.getWriter().println(message);
        } else {
            String message = "Replica is active(host=" + host + ", collection=" + collection + ", shard=" + shard + ")";
            logger.info(message);
            resp.getWriter().println(message);
        }
    }

}

After all these is done, we can easily run maven command to debug and run the things
>mvn jetty:run

Good idea from my colleague, he thinks that we should run that not on maven plugin, but real jetty.
Here is the Makefile>
IMAGE=odt/solr-healthcheck
TAG=latest
NAME=solr-healthcheck
REPOSITORY=sillycat.dkr.ecr.us-east-1.amazonaws.com

# Docker Image

docker-context: target/solr-healthcheck.war

build: docker-context
    docker build -t $(IMAGE):$(TAG) .

debug:
    docker run -ti -p 8080:8080 --name $(NAME) $(IMAGE):$(TAG) /bin/bash

run:
    docker run -p 8080:8080 --name $(NAME) $(IMAGE):$(TAG)

clean:
- docker stop ${NAME}
- docker rm ${NAME}
mvn clean

target/solr-healthcheck.war:
mvn compile package

tag:
docker tag $(IMAGE):$(TAG) $(REPOSITORY)/$(IMAGE):$(TAG)

push:
docker push $(REPOSITORY)/$(IMAGE):$(TAG)

Here is the Dockerfile>
FROM      jetty:9.4.7

COPY      start.sh /var/lib/jetty
COPY      target/solr-healthcheck.war /var/lib/jetty/webapps

ENV       JAVA_OPTIONS=-Xmx64m

CMD       ["./start.sh"]

Here is the start.sh>
#!/bin/sh -ex

# Configuration
HOST_IP=${HOST_IP:-`curl "http://169.254.169.254/latest/meta-data/local-ipv4"`}
COLLECTION=${COLLECTION:-"allJobs"}
SHARD=${SHARD:-"shard1"}

JVM_PROPS="-Dhost=${HOST_IP} -Dcollection=${COLLECTION} -Dshard=${SHARD}"

java -jar /usr/local/jetty/start.jar ${JVM_PROPS}

Beside the Jetty Java Servlet, we can also directly use JAVA HTTP Server like these:
https://www.codeproject.com/Tips/1040097/Create-a-Simple-Web-Server-in-Java-HTTP-Server
https://stackoverflow.com/questions/3732109/simple-http-server-in-java-using-only-java-se-api


References:
http://www.javawebtutor.com/articles/maven/maven_web_project.php
https://github.com/mitreid-connect/simple-web-app/blob/master/pom.xml
http://www.baeldung.com/deploy-to-jetty