Class StringTemplateLoader

  • All Implemented Interfaces:
    TemplateLoader

    public class StringTemplateLoader
    extends Object
    implements TemplateLoader
    A TemplateLoader that uses a Map with Strings as its source of templates. In most case the regular way of loading templates from files will be fine. However, there can be situations where you don't want to or can't load a template from a file, e.g. if you have to deploy a single jar for JavaWebStart or if they are contained within a database. A single template can be created manually e.g.
       String templateStr="Hello ${user}";
       Template t = new Template("name", new StringReader(templateStr),
                   new Configuration());
     
    If, however, you want to create templates from strings which import other templates this method doesn't work. In that case you can create a StringTemplateLoader and add each template to it:
       StringTemplateLoader stringLoader = new StringTemplateLoader();
       stringLoader.putTemplate("greetTemplate", "<#macro greet>Hello</#macro>");
       stringLoader.putTemplate("myTemplate", "<#include \"greetTemplate\"><@greet/> World!");
     
    Then you tell your Configuration object to use it:
       cfg.setTemplateLoader(stringLoader);
     
    After that you should be able to use the templates as usual. Often you will want to combine a StringTemplateLoader with another loader. You can do so using a MultiTemplateLoader.
    • Constructor Detail

      • StringTemplateLoader

        public StringTemplateLoader()
    • Method Detail

      • putTemplate

        public void putTemplate​(String name,
                                String templateSource)
        Puts a template into the loader. A call to this method is identical to the call to the three-arg putTemplate(String, String, long) passing System.currentTimeMillis() as the third argument.
        Parameters:
        name - the name of the template.
        templateSource - the source code of the template.
      • putTemplate

        public void putTemplate​(String name,
                                String templateSource,
                                long lastModified)
        Puts a template into the loader. The name can contain slashes to denote logical directory structure, but must not start with a slash. If the method is called multiple times for the same name and with different last modified time, the configuration's template cache will reload the template according to its own refresh settings (note that if the refresh is disabled in the template cache, the template will not be reloaded). Also, since the cache uses lastModified to trigger reloads, calling the method with different source and identical timestamp won't trigger reloading.
        Parameters:
        name - the name of the template.
        templateSource - the source code of the template.
        lastModified - the time of last modification of the template in terms of System.currentTimeMillis()
      • findTemplateSource

        public Object findTemplateSource​(String name)
        Description copied from interface: TemplateLoader
        Finds the template in the backing storage and returns an object that identifies the storage location where the template can be loaded from. See the return value for more information.
        Specified by:
        findTemplateSource in interface TemplateLoader
        Parameters:
        name - The name of the template, already localized and normalized by the cache. It is completely up to the loader implementation to interpret the name, however it should expect to receive hierarchical paths where path components are separated by a slash (not backslash). Backslashes (or any other OS specific separator character) are not considered as separators by FreeMarker, and thus they will not be replaced with slash before passing to this method, so it's up to the template loader to handle them (say, be throwing and exception that tells the user that the path (s)he has entered is invalid, as (s)he must use slash -- typical mistake of Windows users). The passed names are always considered relative to some loader-defined root location (often referred as the "template root directory"), and will never start with a slash, nor will they contain a path component consisting of either a single or a double dot -- these are all resolved by the template cache before passing the name to the loader. As a side effect, paths that trivially reach outside template root directory, such as ../my.ftl, will be rejected by the template cache, so they never reach the template loader. Note again, that if the path uses backslash as path separator instead of slash as (the template loader should not accept that), the normalization will not properly happen, as FreeMarker (the cache) recognizes only the slashes as separators.
        Returns:
        An object representing the template source, which can be supplied in subsequent calls to TemplateLoader.getLastModified(Object) and TemplateLoader.getReader(Object, String), when those are called on the same TemplateLoader. null must be returned if the source for the template doesn't exist; don't throw exception then! The exact type of this object is up to the TemplateLoader implementation. As this object is possibly used as hash key in caches, and is surly compared with another template source for equality, it must have a proper Object.equals(Object) and Object.hashCode()) implementation. Especially, template sources that refer to the same physical source must be equivalent, otherwise template caching can become inefficient. This is only expected from Object.equals(Object) when the compared template sources came from the same TemplateLoader instance. Also, it must not influence the equality if the source is open or closed (TemplateLoader.closeTemplateSource(Object)).
      • getReader

        public Reader getReader​(Object templateSource,
                                String encoding)
        Description copied from interface: TemplateLoader
        Returns the character stream of a template represented by the specified template source. This method is possibly called for multiple times for the same template source object, and it must always return a Reader that reads the template from its beginning. Before this method is called for the second time (or later), its caller must close the previously returned Reader, and it must not use it anymore. That is, this method is not required to support multiple concurrent readers for the same source templateSource object.

        Typically, this method is called if the template is missing from the cache, or if after calling TemplateLoader.findTemplateSource(String) and TemplateLoader.getLastModified(Object) it was determined that the cached copy of the template is stale. Then, if it turns out that the encoding parameter used doesn't match the actual template content (based on the #ftl encoding=... header), this method will be called for a second time with the correct encoding parameter value.

        Specified by:
        getReader in interface TemplateLoader
        Parameters:
        templateSource - an object representing a template source, obtained through a prior call to TemplateLoader.findTemplateSource(String). This must be an object on which TemplateLoader.closeTemplateSource(Object) wasn't applied yet.
        encoding - the character encoding used to translate source bytes to characters. Some loaders may not have access to the byte representation of the template stream, and instead directly obtain a character stream. These loaders should ignore the encoding parameter.
        Returns:
        A Reader representing the template character stream. It's the responsibility of the caller (which is TemplateCache usually) to close() it. The Reader is not required to work after the templateSource was closed (TemplateLoader.closeTemplateSource(Object)).
      • toString

        public String toString()
        Show class name and some details that are useful in template-not-found errors.
        Overrides:
        toString in class Object
        Since:
        2.3.21