Caucho Technology
  • resin 4.0
  • 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.


    Servlet/Filter initialization

    EL expressions can be used to configure servlets and filters. init-param values can use JSP EL expressions, including the ability to use system properties.

    Servlets, filters, and resources can be configured like beans with setter methods are called directly (See Bean-style init).

    One example use for the bean-style servlet initialization is to avoid JNDI lookup inside the servlet code. For example, a servlet that that uses a JDBC DataSource might look like:

    Servlet using JDBC
    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;

    The servlet is configured as follows:

    Example configuration
      <servlet servlet-name='test'

    The <data-source> xml tag corresponds to the setDataSource method of the bean. More infomation on this powerful pattern is in the bean configuration section of the documentation.

    Environment variables

    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])
    formatthe format string (see below)required
    arg1..argNthe values used for the conversions in the format stringn/a

    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:


    TYPE is required, the rest are optional.

    The following TYPE's are supported:

    %%a percent sign
    %ca character with the given number
    %sa string, a null string becomes "#null"
    %za string, a null string becomes the empty string ""
    %da signed integer, in decimal
    %oan integer, in octal
    %uan integer, in decimal
    %xan integer, in hexadecimal
    %Xan integer, in hexadecimal using upper-case letters
    %ea floating-point number, in scientific notation
    %Ea floating-point number, like %e with an upper-case "E"
    %fa floating-point number, in fixed decimal notation
    %ga floating-point number, in %e or %f notation
    %Ga floating-point number, like %g with an upper-case "E"
    %pa pointer (outputs a value like the default of toString())

    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:

    0If the TYPE character is an integer leading zeroes are used to pad the field width instead of spaces (following any indication of sign or base).
    +Include a `+' with positive numbers.
    (a space)use a space placeholder for the `+' that would result from a positive number
    -The result of is left justified, and the right is padded with blanks until the result is `WIDTH' in length. If you do not use this flag, the result is right justified, and padded on the left.
    #an alternate display is used, for `x' and `X' a non-zero result will have an "0x" prefix; for floating point numbers the result will always contain a decimal point.
    jescape a string suitable for a Java string, or a CSV file. The following escapes are applied: " becomes \", newline becomes \n, return becomes \r, \ becomes \\.
    vescape a string suitable for CSV files, the same as `j' with an additional " placed at the beginning and ending of the string
    mescape a string suitable for a XML file. The following escapes are applied: < becomes &lt;, > becomes &gt; & becomes &amp; ' becomes &#039, " becomes &034;

    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.

    formatthe format string (see below)required
    datean object with java.util.Date or java.util.Calendar or com.caucho.util.QDatethe current date and time
    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.

    %aday of week (short)
    %Aday of week (verbose)
    %bday of month (short)
    %Bday of month (verbose)
    %cJava locale date
    %dday of month (two-digit)
    %H24-hour (two-digit)
    %I12-hour (two-digit)
    %jday of year (three-digit)
    %mmonth (two-digit)
    %Wweek in year (three-digit)
    %wday of week (one-digit)
    %yyear (two-digit)
    %Yyear (four-digit)
    %Ztime zone (name)
    %ztime zone (+/-0800)


    host properties
    nameThe name of the host
    regexpRegular expression values for host regexp matches
    rootThe root directory of the host
    urlThe canonical url of the host


    <host regexp="www.([^.]+).com">
      <context-param server-id="${}"/>
      <web-app id="/">


    java properties
    versionThe JDK version


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

    configuring JNDI
    <servlet servlet-name='foo'


    resin properties
    addressThe local IP address
    confPath to the configuration file
    homeThe the location of the Resin executables
    hostNameThe local hostname as returned by InetAddress
    rootThe location of the content, specified at startup with --root-directory
    serverIdThe identity of the active <server>, specified at startup with --server
    versionThe resin version, e.g. 3.1.0


    Values related to the active <>.

    server properties
    addressthe bind address of the cluster and load balancing port
    idThe identity of the active <server>, specified at startup with --server
    portthe cluster and load balancing port
    httpAddressthe bind address of the http listener, INADDR_ANY for all addresses
    httpPortthe port number of the http listener
    httpsAddressthe bind address of the ssl http listener, INADDR_ANY for all addresses
    httpsPortthe port number of the ssl http listener

    System properties

    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['']}.

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

    Standard system properties
    VARIABLEMEANING temp file path
    os.nameOperating system name
    os.archOperating system architecture
    os.versionOperating system version
    user.nameUser's account name
    user.homeUser's home directory
    user.dirUser's current working directory


    webApp properties
    nameThe name of the web-app
    contextPathThe context path of the web-app
    regexpRegular expression values for web-app regexp matches
    rootThe root directory of the web-app
    urlThe canonical url of the web app

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