el variables and functions

Resin configuration can directly access Resin-IoC/WebBeans-configured beans and variables using EL expressions in the configuration files. Predefines variables include webApp, host, and resin variables.

package test;

...

public class TestServlet extends HttpServlet {
  private DataSource _dataSource;

  /**
   * Bean setter is called to configure the servlet
   * before the init() method.
   */
  public void setDataSource(DataSource dataSource)
  {
    _dataSource = dataSource;
  }

  ...
}

<web-app>
  <allow-servlet-el/>

  <servlet servlet-name='test'
           servlet-class='test.TestServlet'>
    <init>
      <data-source>${jndi("java:comp/env/jdbc/test")}</data-source>
    </init>
  </servlet>

  ...
</web-app>

Environment variables inherited by the process from the operting system are available as variables in el expressions, for example ${LANG}.

Format a string using a sprintf-like format string.

fmt.sprintf(format[,arg1, arg2 ... argN])

sprintf accepts a series of arguments, applies to each a format specifier from `format', and returns the formatted data as a string. `format' is a string containing two types of objects: ordinary characters (other than `%'), which are copied unchanged to the output, and conversion specifications, each of which is introduced by `%'. (To include `%' in the output, use `%%' in the format string).

A conversion specification has the following form:

%[FLAGS][WIDTH][.PREC][TYPE]

TYPE is required, the rest are optional.

The following TYPE's are supported:

Intepret the word `integer' to mean the java type long. Since java does not support unsigned integers, all integers are treated the same.

The following optional FLAGS are supported:

The optional WIDTH argument specifies a minium width for the field. Spaces are used unless the `0' FLAG was used to indicate 0 padding.

The optional PREC argument is introduced with a `.', and gives the maximum number of characters to print; or the minimum number of digits to print for integer and hex values; or the maximum number of significant digits for `g' and `G'; or the number of digits to print after the decimal point for floating points.

Format a timestamp string.

fmt.timestamp(format[,date])

msg="The current date and time is ${fmt.timestamp('%Y/%m/%d %H:%M:%S.%s')}"
msg="time=${fmt.timestamp('[%Y/%m/%d %H:%M:%S.%s]')}"

format contains regular characters, which are just copied to the output string, and percent codes which are substituted with time and date values.

<host regexp="www.([^.]+).com">
  <root-directory>/opt/www/${host.regexp[1]}</root-directory>

  <context-param server-id="${server.name}"/>

  <web-app id="/">
    <document-directory>webapps/ROOT</document-directory>
  </web-app>
</host>

The configuration EL supports the static function jndi:lookup. jndi:lookup can be used to lookup a JNDI value for the configuration.

<servlet servlet-name='foo'
         servlet-class='qa.FooServlet'>
  <init>
    <data-source>${jndi:lookup("java:comp/env/jdbc/test")}</data-source>
  </init>
</servlet>

Values related to the active <>.

System properties are available as variables in el expressions. Many system property names are not valid el identifiers; in that case the system variable is used, for example ${system['java.io.tmpdir']}.

A full list of standard java system properties is provided in the javadoc for java.lang.System.