Package freemarker.cache

Class StringTemplateLoader

java.lang.Object
freemarker.cache.StringTemplateLoader
All Implemented Interfaces:
TemplateLoader
public class StringTemplateLoader extends Object implements TemplateLoader
A TemplateLoader that uses a Map with String-s 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 Details

    • StringTemplateLoader

      public StringTemplateLoader()

  • Method Details

    • putTemplate

      public void putTemplate​(String name, String templateContent)
      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.

      Note that this method is not thread safe! Don't call it after FreeMarker has started using this template loader.

      Parameters:
      name - the name of the template.
      templateContent - the source code of the template.

    • putTemplate

      public void putTemplate​(String name, String templateContent, 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.

      Note that this method is not thread safe! Don't call it after FreeMarker has started using this template loader.

      Parameters:
      name - the name of the template.
      templateContent - the source code of the template.
      lastModified - the time of last modification of the template in terms of System.currentTimeMillis()

    • removeTemplate

      public boolean removeTemplate​(String name)
      Removes the template with the specified name if it was added earlier.

      Note that this method is not thread safe! Don't call it after FreeMarker has started using this template loader.

      Parameters:
      name - Exactly the key with which the template was added.
      Returns:
      Whether a template was found with the given key (and hence was removed now)
      Since:
      2.3.24

    • closeTemplateSource

      public void closeTemplateSource​(Object templateSource)
      Description copied from interface: TemplateLoader
      Closes the template source, releasing any resources held that are only required for reading the template and/or its metadata. This is the last method that is called by the TemplateCache for a template source, except that Object.equals(Object) is might called later too. TemplateCache ensures that this method will be called on every object that is returned from TemplateLoader.findTemplateSource(String).
      Specified by:
      closeTemplateSource in interface TemplateLoader
      Parameters:
      templateSource - the template source that should be closed.

    • 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 (template root directory relative path) 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, by throwing an 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)).

    • getLastModified

      public long getLastModified​(Object templateSource)
      Description copied from interface: TemplateLoader
      Returns the time of last modification of the specified template source. This method is called after findTemplateSource().
      Specified by:
      getLastModified in interface TemplateLoader
      Parameters:
      templateSource - an object representing a template source (the template file), obtained through a prior call to TemplateLoader.findTemplateSource(String). This must be an object on which TemplateLoader.closeTemplateSource(Object) wasn't applied yet.
      Returns:
      The time of last modification for the specified template source, or -1 if the time is not known. This value meant to be milliseconds since the epoch, but in fact FreeMarker doesn't care what it means, it only cares if it changes, in which case the template needs to be reloaded (even if the value has decreased). -1 is not special in that regard either; if you keep returning it, FreeMarker won't reload the template (as far as it's not evicted from the cache from some other reason). Note that Long.MIN_VALUE is reserved for internal use.

    • 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.

      Unlike TemplateLoader.findTemplateSource(String), this method must not tolerate if the template is not found, and must throw IOException in that case.

      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; not null. 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