Dockerize a Java web app from a war file.
Filename: wolves.war
Create a Dockerfile in the same folder as follows:
FROM tomcat:9-jdk11
COPY wolves.war /usr/local/tomcat/webapps/ROOT.war
EXPOSE 8080
CMD ["catalina.sh","run"]
Build a Docker image and run a container
docker build -t javawar .
docker run -dit -p 8080:8080 –name warserv javawar
To access the web application read the content of a file called web.xml at /usr/local/tomcat/webapps/ROOT/WEB-INF in the docker container.
web.xml
<web-app>
<servlet>
<servlet-name>Hello</servlet-name>
<servlet-class>org.apurwa.Hello</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
The URL mapped is /hello thus our access path is:
localhost:8080/hello
Dockerize a Java standalone app from a jar file.
Filename: Hello.jar
Create a Dockerfile as follows:
From openjdk:17-jre-slim
WORKDIR /app
COPY Hello.jar .
CMD ["java", "-jar", "Hello.jar"]
Build a Docker image and run a container
docker build -t javajars .
docker run –rm javajars
Dockerize a java app from a single java file
Hello.java
public class Hello{
public static void main(String[] args){
System.out.println("Java sucks.");
}
}
Create a Dockerfile as follows in the same folder:
FROM openjdk:11-jdk-slim
WORKDIR /app
COPY Hello.java /app
RUN javac Hello.java
CMD ["java","Hello"]
Build Docker image and run the Docker container
docker build -t standjava .
docker run --name standserv standjava
Dockerize a java web app from source code using WAR file
Source code
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Hello.java
package org.apurwa;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Hello extends HttpServlet{
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
response.setContentType("text/html");
response.getWriter().println("<h1>Java sucks!</h1>");
}
}
web.xml
<web-app>
<servlet>
<servlet-name>Hello</servlet-name>
<servlet-class>org.apurwa.Hello</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
pom.xml
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>org.apurwa</groupId>
<artifactId>webjava</artifactId>
<packaging>war</packaging>
<version>1</version>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>11</source>
<target>11</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.3.2</version>
<configuration>
<warName>ROOT</warName>
</configuration>
</plugin>
</plugins>
</build>
</project>
Create a Dockerfile in the root directory as follows:
FROM maven:3.8.4-openjdk-11 AS builder
WORKDIR /app
COPY pom.xml .
COPY src ./src
RUN mvn clean package
FROM tomcat:9.0-jdk11-openjdk-slim
COPY --from=builder /app/target/ROOT.war /usr/local/tomcat/webapps/
EXPOSE 8080
CMD ["catalina.sh", "run"]
Build the Docker image and run a container:
docker build -t javawar .
docker run -dit -p 5000:8080 --name webjserv javawar
The war file is called wolves and the servlet is mapped to /hello. Thus the access path is:
http://localhost:5000/hello