freemarker.cache
Interface TemplateLoader

All Known Subinterfaces:

StatefulTemplateLoader

All Known Implementing Classes:

ClassTemplateLoader, FileTemplateLoader, MultiTemplateLoader, StringTemplateLoader, URLTemplateLoader, WebappTemplateLoader

public interface TemplateLoader

A template loader is an object that can find the source stream for a template, can retrieve its time of last modification as well as the stream itself. A template loader is plugged into the TemplateCache to provide concrete loading of the templates. The implementations can be coded in a non-threadsafe manner as the natural user of the template loader, TemplateCache does the necessary synchronization.

Version:

$Id: TemplateLoader.java,v 1.18 2004/03/01 01:13:30 ddekany Exp $

Author:

Attila Szegedi, szegedia at freemail dot hu

Method Summary

void	closeTemplateSource(java.lang.Object templateSource) Closes the template source.
java.lang.Object	findTemplateSource(java.lang.String name) Finds the object that acts as the source of the template with the given name.
long	getLastModified(java.lang.Object templateSource) Returns the time of last modification of the specified template source.
java.io.Reader	getReader(java.lang.Object templateSource, java.lang.String encoding) Returns the character stream of a template represented by the specified template source.

Method Detail

findTemplateSource

java.lang.Object findTemplateSource(java.lang.String name)
                                    throws java.io.IOException

Finds the object that acts as the source of the template with the given name. This method is called by the TemplateCache when a template is requested, before calling either getLastModified(Object) or getReader(Object, String).

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 is 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 reffered as the "template root direcotry"), 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 normalisation 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 getLastModified(Object) and getReader(Object, String). Null must be returned if the source for the template can not be found (do not throw FileNotFoundException!). The returned object may will be compared with a cached template source object for equality, using the equals method. Thus, objects returned for the same physical source must be equivalent according to equals method, otherwise template caching can become very ineffective!

Throws:

java.io.IOException

getLastModified

long getLastModified(java.lang.Object templateSource)

Returns the time of last modification of the specified template source. This method is called after findTemplateSource().

Parameters:

templateSource - an object representing a template source, obtained through a prior call to findTemplateSource(String).

Returns:

the time of last modification of the specified template source, or -1 if the time is not known.

getReader

java.io.Reader getReader(java.lang.Object templateSource,
                         java.lang.String encoding)
                         throws java.io.IOException

Returns the character stream of a template represented by the specified template source. This method is called after getLastModified() if it is determined that a cached copy of the template is unavailable or stale.

Parameters:

templateSource - an object representing a template source, obtained through a prior call to findTemplateSource(String).

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 will - quite naturally - ignore the encoding parameter.

Returns:

a reader representing the template character stream. The framework will call close().

Throws:

java.io.IOException - if an I/O error occurs while accessing the stream.

closeTemplateSource

void closeTemplateSource(java.lang.Object templateSource)
                         throws java.io.IOException

Closes the template source. This is the last method that is called by the TemplateCache for a templateSource. The framework guarantees that this method will be called on every object that is returned from findTemplateSource(String).

Parameters:

templateSource - the template source that should be closed.

Throws:

java.io.IOException