Launch Docker from Java to convert Office documents to PDF

1.First of all

• The operating environment is for docker on CentOS7.
• It has been confirmed that it does not work well with docker on Windows.
• Java version confirmed in 1.8

2. Install Docker

Install Docker on CentOS. See official page for details https://docs.docker.com/engine/installation/linux/docker-ce/centos/

yum install -y yum-utils \
  device-mapper-persistent-data \
  lvm2
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
yum makecache fast
yum install docker-ce
systemctl enable docker
systemctl start docker

3. Docker settings

(1). Build an image of CentOS7

docker pull centos:centos7
docker run -it centos:centos7 /bin/bash

(2). Introduce LibreOffice and IPA font

yum update -y
yum install libreoffice* ipa-*-fonts

(3). Create a working folder

mkdir /tmp/
exit

(4). Check the Docker CONTAINER ID

docker ps -a

(5). Commit with the name "office" Enter the CONTAINER ID confirmed earlier in * $ {CONTAINER ID} *.

docker commit ${CONTAINER ID} office

(6). Check if it works properly It is assumed that the "/var/tmp/test.xlsx" file exists on CentOS. If executed normally, "/var/tmp/test.pdf" will be generated.

docker run --rm=true -it -v /var/tmp:/tmp office libreoffice --headless --nologo --nofirststartwizard --convert-to pdf --outdir /tmp /tmp/test.xlsx

4. Java coding

This is a sample to start docker with java process class.

	/**
	 *Convert PDF via Docker
	 * @param excelFileName
	 * @param pdfFileName
	 * @return
	 * @throws InterruptedException
	 */
    public boolean convertPDF(String excelFileName) throws InterruptedException {

		//Start command specification
		String[] command = {
				"docker", "run", "--rm=true", "-v", "/var/tmp:/tmp", "office", "libreoffice", "--headless"
                , "--nologo", "--nofirststartwizard", "--convert-to", "pdf", "--outdir"
                ,"/tmp", "/tmp/"+excelFileName };

        ProcessBuilder pb = new ProcessBuilder(command);

		try {
            //Command execution
			Process process = pb.start();

            //Wait for the result of command execution
			int ret = process.waitFor();

            //Standard output
			InputStream is = process.getInputStream();	
			printInputStream(is);

            //Standard error
			InputStream es = process.getErrorStream();	
			printInputStream(es);

		}
		catch (Exception e) {
			return false;

		}

		return true;
    }
    
	/**
	 *Display standard error output
	 * @param is
	 * @throws IOException
	 */
    public static void printInputStream(InputStream is) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(is));
		try {
			for (;;) {
				String line = br.readLine();
				if (line == null) break;
				System.out.println(line);
			}
		} finally {
			br.close();
		}
	}