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+++ title = "Prerequisites" weight = 10 +++
The two components have one prerequisite in common: they both require Java to run. While this is the only requirement for the REST server, the Joex components requires some more external programs.
The rest server and joex components are not required to "see" each other, though it is recommended.
Java
Very often, Java is already installed. You can check this by opening a
terminal and typing java -version. Otherwise install Java using your
package manager or see this site for
other options.
It is enough to install the JRE. The JDK is required, if you want to build docspell from source. For newer versions, the JRE is not shipped anymore, simply use JDK then.
Docspell has been tested with Java version 1.8 (or sometimes referred to as JRE 8 and JDK 8, respectively). The pre-build packages are build using JDK 8. So at least a JDK/JRE 8 is required. However, it also works on newer java versions, I recommend JDK 11 as this has better default options. The provided docker images use JDK11, too.
The next tools are only required on machines running the Joex component.
External Programs for Joex
- Ghostscript (the
gscommand) is used to extract/convert PDF files into images that are then fed to ocr. It is available on most GNU/Linux distributions. - Unpaper is a program that pre-processes images to yield better results when doing ocr. If this is not installed, docspell tries without it. However, it is recommended to install, because it improves text extraction (at the expense of a longer runtime).
- Tesseract is the tool doing the OCR (converts images into text). It can also convert images into pdf files. It is a widely used open source OCR engine. Tesseract 3 and 4 should work with docspell; you can adopt the command line in the configuration file, if necessary.
- Unoconv is used to convert office documents into PDF files. It uses libreoffice/openoffice.
- wkhtmltopdf is used to convert HTML into PDF files.
- OCRmyPDF can be optionally used to convert PDF to PDF files. It adds an OCR layer to scanned PDF files to make them searchable. It also creates PDF/A files from the input pdf.
The performance of unoconv can be improved by starting unoconv -l
in a separate process. This runs a libreoffice/openoffice listener and
therefore avoids starting one each time unoconv is called.
Example Debian
On Debian this should install all joex requirements:
sudo apt-get install ghostscript tesseract-ocr tesseract-ocr-deu tesseract-ocr-eng unpaper unoconv wkhtmltopdf ocrmypdf
Apache SOLR
SOLR is used to provide the fulltext search feature. This feature can be disabled, so installing SOLR is optional. But without it, there is no fulltext search.
When installing manually (i.e. not via docker), just install solr and create a core as described in the solr documentation. That will provide you with the connection url (the last part is the core name).
When using the provided docker-compose.yml setup, SOLR is already setup.
SOLR must be reachable from all joex and all rest server components.
Database
Both components must have access to a SQL database. The SQL database contains all data (including binary files) and is the central component of docspell. Docspell has support these databases:
- PostreSQL
- MariaDB
- H2
The H2 database is an interesting option for personal and mid-size setups, as it requires no additional work. It is integrated into docspell and works really well out of the box. It is also configured as the default database.
When using H2, make sure that all components access the same database
– the jdbc url must point to the same file. Then, it is important to
add the options
;MODE=PostgreSQL;DATABASE_TO_LOWER=TRUE;AUTO_SERVER=TRUE at the end
of the url. See the config page for
an example.
For large installations, PostgreSQL or MariaDB is recommended. Create a database and a user with enough privileges (read, write, create table) to that database.