Package freemarker.ext.servlet

Class FreemarkerServlet

  • All Implemented Interfaces:
    Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig
    public class FreemarkerServlet
extends javax.servlet.http.HttpServlet
    FreeMarker MVC View servlet that can be used similarly to JSP views. That is, you put the variables to expose into HTTP servlet request attributes, then forward to an FTL file (instead of to a JSP file) that's mapped to this servet (usually via the <url-pattern>*.ftl<url-pattern>). See web.xml example (and more) in the FreeMarker Manual!

    Main features

    • It makes all request, request parameters, session, and servlet context attributes available to templates through Request, RequestParameters, Session, and Application variables.
    • The scope variables are also available via automatic scope discovery. That is, writing Application.attrName, Session.attrName, Request.attrName is not mandatory; it's enough to write attrName, and if no such variable was created in the template, it will search the variable in Request, and then in Session, and finally in Application.
    • It creates a variable with name JspTaglibs that can be used to load JSP taglibs. For example:
      <#assign dt=JspTaglibs["http://displaytag.sf.net"]> or <#assign tiles=JspTaglibs["/WEB-INF/struts-tiles.tld"]>.
    • A custom directive named include_page allows you to include the output of another servlet resource from your servlet container, just as if you used ServletRequest.getRequestDispatcher(path).include(): <@include_page path="/myWebapp/somePage.jsp"/>. You can also pass parameters to the newly included page by passing a hash named params: <@include_page path="/myWebapp/somePage.jsp" params= lang: "en", q="5"}/>. By default, the request parameters of the original request (the one being processed by FreemarkerServlet) are also inherited by the include. You can explicitly control this inheritance using the inherit_params parameter: <@include_page path="/myWebapp/somePage.jsp" params={lang: "en", q="5"} inherit_params=false/>.

    Supported init-param-s

    • "TemplatePath": Specifies the location of the templates. By default, this is interpreted as a ServletContext reasource path, which practically means a web application directory relative path, or a WEB-INF/lib/*.jar/META-INF/resources-relative path (note that this last didn't work properly before FreeMarker 2.3.23).
      Alternatively, you can prepend it with file:// to indicate a literal path in the file system (i.e. file:///var/www/project/templates/). Note that three slashes were used to specify an absolute path.
      Also, you can prepend it with classpath:, like in classpath:com/example/templates, to indicate that you want to load templates from the specified package accessible through the Thread Context Class Loader of the thread that initializes this servlet.
      If incompatible_improvements is set to 2.3.22 (or higher), you can specify multiple comma separated locations inside square brackets, like: [ WEB-INF/templates, classpath:com/example/myapp/templates ]. This internally creates a MultiTemplateLoader. Note again that if incompatible_improvements isn't set to at least 2.3.22, the initial [ has no special meaning, and so this feature is unavailable.
      Any of the above can have a ?setting(name=value, ...) postfix to set the JavaBeans properties of the TemplateLoader created. For example, /templates?settings(attemptFileAccess=false, URLConnectionUsesCaches=true) calls WebappTemplateLoader.setAttemptFileAccess(boolean) and WebappTemplateLoader.setURLConnectionUsesCaches(Boolean) to tune the WebappTemplateLoader. For backward compatibility (not recommended!), you can use the class:// prefix, like in class://com/example/templates format, which is similar to classpath:, except that it uses the defining class loader of this servlet's class. This can cause template not found errors, if that class (in freemarer.jar usually) is not local to the web application, while the templates are.
      The default value is class:// (that is, the root of the class hierarchy), which is not recommended anymore, and should be overwritten with the init-param.
    • "NoCache": If set to true, generates headers in the response that advise the HTTP client not to cache the returned page. The default is false.
    • "ContentType": If specified, response uses the specified Content-type HTTP header. The value may include the charset (e.g. "text/html; charset=ISO-8859-1"). If not specified, "text/html" is used. If the charset is not specified in this init-param, then the charset (encoding) of the actual template file will be used (in the response HTTP header and for encoding the output stream). Note that this setting can be overridden on a per-template basis by specifying a custom attribute named content_type in the attributes parameter of the <#ftl> directive.
    • "BufferSize": Sets the size of the output buffer in bytes, or if "KB" or "MB" is written after the number (like <param-value>256 KB</param-value>) then in kilobytes or megabytes. This corresponds to ServletResponse.setBufferSize(int). If the HttpServletResponse state doesn't allow changing the buffer size, it will silently do nothing. If this init param isn't specified, then the buffer size is not set by FreemarkerServlet in the HTTP response, which usually means that the default buffer size of the servlet container will be used.
    • "ExceptionOnMissingTemplate" (since 2.3.22): If false (default, but not recommended), if a template is requested that's missing, this servlet responses with a HTTP 404 "Not found" error, and only logs the problem with debug level. If true (recommended), the servlet will log the issue with error level, then throws an exception that bubbles up to the servlet container, which usually then creates a HTTP 500 "Internal server error" response (and maybe logs the event into the container log). See "Error handling" later for more!
    • "MetaInfTldSources" (since 2.3.22): Comma separated list of items, each is either "webInfPerLibJars", or "classpath" optionally followed by colon and a regular expression, or "clear". For example <param-value>classpath:.*myoverride.*\.jar$, webInfPerLibJars, classpath:.*taglib.*\.jar$</param-value>, or <param-value>classpath</param-value>. (Whitespace around the commas and list items will be ignored.) See TaglibFactory.setMetaInfTldSources(List) for more information. Defaults to a list that contains "webInfPerLibJars" only (can be overridden with createDefaultMetaInfTldSources()). Note that this can be also specified with the "org.freemarker.jsp.metaInfTldSources" system property. If both the init-param and the system property exists, the sources listed in the system property will be added after those specified by the init-param. This is where the special entry, "clear" comes handy, as it will remove all previous list items. (An intended usage of the system property is setting it to clear, classpath in the Eclipse run configuration if you are running the application without putting the dependency jar-s into WEB-INF/lib.) Also, note that further classpath:<pattern> items are added automatically at the end of this list based on Jetty's "org.eclipse.jetty.server.webapp.ContainerIncludeJarPattern" servlet context attribute.
    • "ClasspathTlds" (since 2.3.22): Comma separated list of paths; see TaglibFactory.setClasspathTlds(List). Whitespace around the list items will be ignored. Defaults to no paths (can be overidden with createDefaultClassPathTlds()). Note that this can also be specified with the "org.freemarker.jsp.classpathTlds" system property. If both the init-param and the system property exists, the items listed in system property will be added after those specified by the init-param.
    • "Debug": Deprecated, has no effect since 2.3.22. (Earlier it has enabled/disabled sending debug-level log messages to the servlet container log, but this servlet doesn't log debug level messages into the servlet container log anymore, only into the FreeMarker log.)
    • The following init-params are supported only for backward compatibility, and their usage is discouraged: TemplateUpdateInterval, DefaultEncoding, ObjectWrapper, TemplateExceptionHandler. Instead, use init-params with the setting names documented at Configuration.setSetting(String, String), such as object_wrapper.
    • Any other init-params will be interpreted as Configuration-level FreeMarker setting. See the possible names and values at Configuration.setSetting(String, String).

    Error handling

    Notes:

    • Logging below, where not said otherwise, always refers to logging with FreeMarker's logging facility (see Logger), under the "freemarker.servlet" category.
    • Throwing a ServletException to the servlet container is mentioned at a few places below. That in practice usually means HTTP 500 "Internal server error" response, and maybe a log entry in the servlet container's log.

    Errors types:

    • If the servlet initialization fails, the servlet won't be started as usual. The cause is usually logged with error level. When it isn't, check the servlet container's log.
    • If the requested template doesn't exist, by default the servlet returns a HTTP 404 "Not found" response, and logs the problem with debug level. Responding with HTTP 404 is how JSP behaves, but it's actually not a recommended setting anymore. By setting "ExceptionOnMissingTemplate" init-param to true (recommended), it will instead log the problem with error level, then the servlet throws ServletException to the servlet container (with the proper cause exception). After all, if the visited URL had an associated "action" but the template behind it is missing, that's an internal server error, not a wrong URL.
    • If the template contains parsing errors, it will log it with error level, then the servlet throws ServletException to the servlet container (with the proper cause exception).
    • If the template throws exception during its execution, and the value of the template_exception_handler init-param is rethrow (recommended), it will log it with error level and then the servlet throws ServletException to the servlet container (with the proper cause exception). But beware, the default value of the template_exception_handler init-param is html_debug, which is for development only! Set it to rethrow for production. The html_debug (and debug) handlers will print error details to the page and then commit the HTTP response with response code 200 "OK", thus, the server wont be able roll back the response and send back an HTTP 500 page. This is so that the template developers will see the error without digging the logs.
    See Also:
    Serialized Form

    • Field Detail

      • INIT_PARAM_TEMPLATE_PATH

        public static final String INIT_PARAM_TEMPLATE_PATH
        Init-param name - see the FreemarkerServlet class documentation about the init-params. (This init-param has existed long before 2.3.22, but this constant was only added then.)
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • INIT_PARAM_NO_CACHE

        public static final String INIT_PARAM_NO_CACHE
        Init-param name - see the FreemarkerServlet class documentation about the init-params. (This init-param has existed long before 2.3.22, but this constant was only added then.)
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • INIT_PARAM_CONTENT_TYPE

        public static final String INIT_PARAM_CONTENT_TYPE
        Init-param name - see the FreemarkerServlet class documentation about the init-params. (This init-param has existed long before 2.3.22, but this constant was only added then.)
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • INIT_PARAM_META_INF_TLD_LOCATIONS

        public static final String INIT_PARAM_META_INF_TLD_LOCATIONS
        Init-param name - see the FreemarkerServlet class documentation about the init-params.
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • INIT_PARAM_EXCEPTION_ON_MISSING_TEMPLATE

        public static final String INIT_PARAM_EXCEPTION_ON_MISSING_TEMPLATE
        Init-param name - see the FreemarkerServlet class documentation about the init-params.
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • SYSTEM_PROPERTY_META_INF_TLD_SOURCES

        public static final String SYSTEM_PROPERTY_META_INF_TLD_SOURCES
        When set, the items defined in it will be added after those coming from the "MetaInfTldSources" init-param. The value syntax is the same as of the init-param. Note that "clear" can be used to re-start the list, rather than continue it.
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • SYSTEM_PROPERTY_CLASSPATH_TLDS

        public static final String SYSTEM_PROPERTY_CLASSPATH_TLDS
        When set, the items defined in it will be added after those coming from the "ClasspathTlds" init-param. The value syntax is the same as of the init-param.
        Since:
        2.3.22
        See Also:
        Constant Field Values

      • debug

        protected boolean debug
        Deprecated.
        Not used anymore; to enable/disable debug logging, just set the logging level of the logging library used by Logger.

    • Constructor Detail

      • FreemarkerServlet

        public FreemarkerServlet()

    • Method Detail

      • init

        public void init()
          throws javax.servlet.ServletException
        Don't override this method to adjust FreeMarker settings! Override the protected methods for that, such as createConfiguration(), createTemplateLoader(String), createDefaultObjectWrapper(), etc. Also note that lot of things can be changed with init-params instead of overriding methods, so if you override settings, usually you should only override their defaults.
        Overrides:
        init in class javax.servlet.GenericServlet
        Throws:
        javax.servlet.ServletException

      • doGet

        public void doGet​(javax.servlet.http.HttpServletRequest request,
                  javax.servlet.http.HttpServletResponse response)
           throws javax.servlet.ServletException,
                  IOException
        Overrides:
        doGet in class javax.servlet.http.HttpServlet
        Throws:
        javax.servlet.ServletException
        IOException

      • doPost

        public void doPost​(javax.servlet.http.HttpServletRequest request,
                   javax.servlet.http.HttpServletResponse response)
            throws javax.servlet.ServletException,
                   IOException
        Overrides:
        doPost in class javax.servlet.http.HttpServlet
        Throws:
        javax.servlet.ServletException
        IOException

      • deduceLocale

        protected Locale deduceLocale​(String templatePath,
                              javax.servlet.http.HttpServletRequest request,
                              javax.servlet.http.HttpServletResponse response)
                       throws javax.servlet.ServletException
        Returns the locale used for the Configuration.getTemplate(String, Locale) call. The base implementation simply returns the locale setting of the configuration. Override this method to provide different behaviour, i.e. to use the locale indicated in the request.
        Parameters:
        templatePath - The template path (templat name) as it will be passed to Configuration.getTemplate(String). (Not to be confused with the servlet init-param of identical name; they aren't related.)
        Throws:
        javax.servlet.ServletException - Can be thrown since 2.3.22, if the locale can't be deduced from the URL.

      • createTaglibFactory

        protected TaglibFactory createTaglibFactory​(ObjectWrapper objectWrapper,
                                            javax.servlet.ServletContext servletContext)
                                     throws TemplateModelException
        Called to create the TaglibFactory once per servlet context. The default implementation configures it based on the servlet-init parameters and various other environmental settings, so if you override this method, you should call super, then adjust the result.
        Throws:
        TemplateModelException
        Since:
        2.3.22

      • requestUrlToTemplatePath

        protected String requestUrlToTemplatePath​(javax.servlet.http.HttpServletRequest request)
                                   throws javax.servlet.ServletException
        Maps the request URL to a template path (template name) that is passed to Configuration.getTemplate(String, Locale). You can override it (i.e. to provide advanced rewriting capabilities), but you are strongly encouraged to call the overridden method first, then only modify its return value.
        Parameters:
        request - The currently processed HTTP request
        Returns:
        The template path (template name); can't be null. This is what's passed to Configuration.getTemplate(String) later. (Not to be confused with the templatePath servlet init-param of identical name; that basically specifies the "virtual file system" to which this will be relative to.)
        Throws:
        javax.servlet.ServletException - Can be thrown since 2.3.22, if the template path can't be deduced from the URL.

      • preprocessRequest

        protected boolean preprocessRequest​(javax.servlet.http.HttpServletRequest request,
                                    javax.servlet.http.HttpServletResponse response)
                             throws javax.servlet.ServletException,
                                    IOException
        Called as the first step in request processing, before the templating mechanism is put to work. By default does nothing and returns false. This method is typically overridden to manage serving of non-template resources (i.e. images) that reside in the template directory.
        Parameters:
        request - the HTTP request
        response - the HTTP response
        Returns:
        true to indicate this method has processed the request entirely, and that the further request processing should not take place.
        Throws:
        javax.servlet.ServletException
        IOException

      • createConfiguration

        protected Configuration createConfiguration()
        Creates the FreeMarker Configuration singleton and (when overidden) maybe sets its defaults. Servlet init-params will be applied later, and thus can overwrite the settings specified here.

        By overriding this method you can set your preferred Configuration setting defaults, as only the settings for which an init-param was specified will be overwritten later. (Note that FreemarkerServlet also has its own defaults for a few settings, but since 2.3.22, the servlet detects if those settings were already set here and then it won't overwrite them.)

        The default implementation simply creates a new instance with Configuration() and returns it.

      • setConfigurationDefaults

        protected void setConfigurationDefaults()
        Sets the defaults of the configuration that are specific to the FreemarkerServlet subclass. This is called after the common (wired in) FreemarkerServlet setting defaults was set, also the

      • createObjectWrapper

        protected ObjectWrapper createObjectWrapper()
        Called from init() to create the ObjectWrapper; to customzie this aspect, in most cases you should override createDefaultObjectWrapper() instead. Overriding this method is necessary when you want to customize how the ObjectWrapper is created from the init-param values, or you want to do some post-processing (like checking) on the created ObjectWrapper. To customize init-param interpretation, call GenericServlet.getInitParameter(String) with Configurable.OBJECT_WRAPPER_KEY as argument, and see if it returns a value that you want to interpret yourself. If was null or you don't want to interpret the value, fall back to the super method.

        The default implementation interprets the object_wrapper servlet init-param with calling Configurable.setSetting(String, String) (see valid values there), or if there's no such servlet init-param, then it calls createDefaultObjectWrapper().

        Returns:
        The ObjectWrapper that will be used for adapting request, session, and servlet context attributes to TemplateModel-s, and also as the object wrapper setting of Configuration.

      • getTemplatePath

        protected final String getTemplatePath()
        Deprecated.
        Not called by FreeMarker code, and there's no point to override this (unless to cause confusion).
        The value of the TemplatePath init-param. null if the template_loader setting was set in a custom createConfiguration().

      • createRequestParametersHashModel

        protected HttpRequestParametersHashModel createRequestParametersHashModel​(javax.servlet.http.HttpServletRequest request)

      • initializeServletContext

        protected void initializeServletContext​(javax.servlet.http.HttpServletRequest request,
                                        javax.servlet.http.HttpServletResponse response)
                                 throws javax.servlet.ServletException,
                                        IOException
        Called when servlet detects in a request processing that application-global (that is, ServletContext-specific) attributes are not yet set. This is a generic hook you might use in subclasses to perform a specific action on first request in the context. By default it does nothing.
        Parameters:
        request - the actual HTTP request
        response - the actual HTTP response
        Throws:
        javax.servlet.ServletException
        IOException

      • initializeSession

        protected void initializeSession​(javax.servlet.http.HttpServletRequest request,
                                 javax.servlet.http.HttpServletResponse response)
                          throws javax.servlet.ServletException,
                                 IOException
        Called when servlet detects in a request processing that session-global (that is, HttpSession-specific) attributes are not yet set. This is a generic hook you might use in subclasses to perform a specific action on first request in the session. By default it does nothing. It is only invoked on newly created sessions; it's not invoked when a replicated session is reinstantiated in another servlet container.
        Parameters:
        request - the actual HTTP request
        response - the actual HTTP response
        Throws:
        javax.servlet.ServletException
        IOException

      • preTemplateProcess

        protected boolean preTemplateProcess​(javax.servlet.http.HttpServletRequest request,
                                     javax.servlet.http.HttpServletResponse response,
                                     Template template,
                                     TemplateModel data)
                              throws javax.servlet.ServletException,
                                     IOException
        Called before the execution is passed to template.process(). This is a generic hook you might use in subclasses to perform a specific action before the template is processed. By default does nothing. A typical action to perform here is to inject application-specific objects into the model root

        Example: Expose the Serlvet context path as "baseDir" for all templates: 

            ((SimpleHash) data).put("baseDir", request.getContextPath() + "/");
    return true;
        Parameters:
        request - the actual HTTP request
        response - the actual HTTP response
        template - the template that will get executed
        data - the data that will be passed to the template. By default this will be an AllHttpScopesHashModel (which is a SimpleHash subclass). Thus, you can add new variables to the data-model with the SimpleHash.put(String, Object) subclass) method.
        Returns:
        true to process the template, false to suppress template processing.
        Throws:
        javax.servlet.ServletException
        IOException

      • postTemplateProcess

        protected void postTemplateProcess​(javax.servlet.http.HttpServletRequest request,
                                   javax.servlet.http.HttpServletResponse response,
                                   Template template,
                                   TemplateModel data)
                            throws javax.servlet.ServletException,
                                   IOException
        Called after the execution returns from template.process(). This is a generic hook you might use in subclasses to perform a specific action after the template is processed. It will be invoked even if the template processing throws an exception. By default does nothing.
        Parameters:
        request - the actual HTTP request
        response - the actual HTTP response
        template - the template that was executed
        data - the data that was passed to the template
        Throws:
        javax.servlet.ServletException
        IOException

      • getConfiguration

        protected Configuration getConfiguration()
        Returns the Configuration object used by this servlet. Please don't forget that Configuration is not thread-safe when you modify it.