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DataSources

A DataSource consists of lazy-loaded data available in Apache FreeMarker’s model (context) - it provides

  • a charset for reading textual content
  • a content type
  • a name and a group
  • access to textual content directly or using a line iterator
  • access to the data input stream

Loading A DataSource

A DataSource can be loaded from the file system, e.g. as positional command line argument

freemarker-cli -t templates/info.ftl README.md

FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=README.md, group=default, contentType=text/markdown, charset=UTF-8, length=57,188 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/README.md

from an URL

freemarker-cli --data-source xkcd=https://xkcd.com/info.0.json -t templates/info.ftl

FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=xkcd, group=default, contentType=application/json, charset=UTF-8, length=-1 Bytes
    URI : https://xkcd.com/info.0.json

or from an environment variable, e.g. NGINX_CONF having a JSON payload

export NGINX_CONF='{"NGINX_PORT":"8443","NGINX_HOSTNAME":"localhost"}'
freemarker-cli -t templates/info.ftl -s conf=env:///NGINX_CONF#mimetype=application/json

FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=conf, group=default, contentType=application/json, charset=UTF-8, length=50 Bytes
    URI : env:///NGINX_CONF

Of course you can load multiple DataSources directly

freemarker-cli -t templates/info.ftl README.md xkcd=https://xkcd.com/info.0.json
 
FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=README.md, group=default, contentType=text/markdown, charset=UTF-8, length=57,188 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/README.md
    [#2], name=xkcd, group=default, contentType=application/json, charset=UTF-8, length=-1 Bytes
    URI : https://xkcd.com/info.0.json

or load them from a directory

freemarker-cli -t templates/info.ftl -s examples/data
FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=combined-access.log, group=default, contentType=text/plain, charset=UTF-8, length=2,068 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/examples/data/accesslog/combined-access.log
    ...
    [#22], name=swagger-spec.yaml, group=default, contentType=text/yaml, charset=UTF-8, length=17,555 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/examples/data/yaml/swagger-spec.yaml

which can be combined with include and exclude filters

freemarker-cli -t templates/info.ftl -s examples/data --data-source-include=*.json

FreeMarker CLI DataSources
------------------------------------------------------------------------------
    [#1], name=github-users.json, group=default, contentType=application/json, charset=UTF-8, length=7,168 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/examples/data/json/github-users.json
    [#2], name=swagger-spec.json, group=default, contentType=application/json, charset=UTF-8, length=24,948 Bytes
    URI : file:/Users/sgoeschl/work/github/apache/freemarker-generator/freemarker-generator-cli/target/appassembler/examples/data/json/swagger-spec.json

Selecting A DataSource

After loading one or more DataSource it needs to be selected for template processing - the DataSources instance exposed in the data model provides

  • Selecting by index
  • Selecting by name
  • Filter by the globbing pattern (see Apache Commons IO)

A few FTL examples

<#assign dataSource = DataSources.get(0)>

<#assign dataSource = DataSources.get("user.csv)>

<#list DataSources.find("*.md") as dataSource>
- ${dataSource.name}
</#list>