org.apache.velocity.app
Class Velocity

java.lang.Object
  org.apache.velocity.app.Velocity

All Implemented Interfaces:

RuntimeConstants

public class Velocity
extends Object
implements RuntimeConstants

This class provides services to the application developer, such as :

• Simple Velocity Runtime engine initialization methods.
• Functions to apply the template engine to streams and strings to allow embedding and dynamic template generation.
• Methods to access Velocimacros directly.

While the most common way to use Velocity is via templates, as Velocity is a general-purpose template engine, there are other uses that Velocity is well suited for, such as processing dynamically created templates, or processing content streams.

The methods herein were developed to allow easy access to the Velocity facilities without direct spelunking of the internals. If there is something you feel is necessary to add here, please, send a patch.

Version:

$Id: Velocity.java 687177 2008-08-19 22:00:32Z nbubna $

Author:

Geir Magnusson Jr., Christoph Reck, Jason van Zyl

Field Summary

Fields inherited from interface org.apache.velocity.runtime.RuntimeConstants

COUNTER_INITIAL_VALUE, COUNTER_NAME, DEBUG_PREFIX, DEFAULT_RUNTIME_DIRECTIVES, DEFAULT_RUNTIME_PROPERTIES, DEFINE_DIRECTIVE_MAXDEPTH, ENCODING_DEFAULT, ERROR_PREFIX, ERRORMSG_END, ERRORMSG_START, EVALUATE_CONTEXT_CLASS, EVENTHANDLER_INCLUDE, EVENTHANDLER_INVALIDREFERENCES, EVENTHANDLER_METHODEXCEPTION, EVENTHANDLER_NULLSET, EVENTHANDLER_REFERENCEINSERTION, FILE_RESOURCE_LOADER_CACHE, FILE_RESOURCE_LOADER_PATH, HAS_NEXT_NAME, INFO_PREFIX, INPUT_ENCODING, INTERPOLATE_STRINGLITERALS, INTROSPECTOR_RESTRICT_CLASSES, INTROSPECTOR_RESTRICT_PACKAGES, MAX_NUMBER_LOOPS, NUMBER_OF_PARSERS, OUTPUT_ENCODING, PARSE_DIRECTIVE_MAXDEPTH, PARSER_POOL_CLASS, PARSER_POOL_SIZE, RESOURCE_LOADER, RESOURCE_MANAGER_CACHE_CLASS, RESOURCE_MANAGER_CLASS, RESOURCE_MANAGER_DEFAULTCACHE_SIZE, RESOURCE_MANAGER_LOGWHENFOUND, RUNTIME_LOG, RUNTIME_LOG_ERROR_STACKTRACE, RUNTIME_LOG_INFO_STACKTRACE, RUNTIME_LOG_LOGSYSTEM, RUNTIME_LOG_LOGSYSTEM_CLASS, RUNTIME_LOG_REFERENCE_LOG_INVALID, RUNTIME_LOG_WARN_STACKTRACE, RUNTIME_REFERENCES_STRICT, SET_NULL_ALLOWED, SKIP_INVALID_ITERATOR, STRICT_MATH, TRACE_PREFIX, UBERSPECT_CLASSNAME, UNKNOWN_PREFIX, VM_ARGUMENTS_STRICT, VM_CONTEXT_LOCALSCOPE, VM_LIBRARY, VM_LIBRARY_AUTORELOAD, VM_LIBRARY_DEFAULT, VM_MAX_DEPTH, VM_MESSAGES_ON, VM_PERM_ALLOW_INLINE, VM_PERM_ALLOW_INLINE_REPLACE_GLOBAL, VM_PERM_INLINE_LOCAL, WARN_PREFIX

Constructor Summary

Velocity()

Method Summary

static void	addProperty(String key, Object value) Add a Velocity Runtime property.
static void	clearProperty(String key) Clear a Velocity Runtime property.
static void	debug(Object message) Deprecated. Use getLog() and call debug() on it.
static void	error(Object message) Deprecated. Use getLog() and call error() on it.
static boolean	evaluate(Context context, Writer writer, String logTag, InputStream instream) Deprecated. Use evaluate( Context context, Writer writer, String logTag, Reader reader )
static boolean	evaluate(Context context, Writer writer, String logTag, Reader reader) Renders the input reader using the context into the output writer.
static boolean	evaluate(Context context, Writer out, String logTag, String instring) renders the input string using the context into the output writer.
static Log	getLog() Returns a convenient Log instance that wraps the current LogChute.
static Object	getProperty(String key) Get a Velocity Runtime property.
static Template	getTemplate(String name) Returns a Template from the Velocity resource management system.
static Template	getTemplate(String name, String encoding) Returns a Template from the Velocity resource management system.
static void	info(Object message) Deprecated. Use getLog() and call info() on it.
static void	init() initialize the Velocity runtime engine, using the default properties of the Velocity distribution
static void	init(Properties p) initialize the Velocity runtime engine, using default properties plus the properties in the passed in java.util.Properties object
static void	init(String propsFilename) initialize the Velocity runtime engine, using default properties plus the properties in the properties file passed in as the arg
static boolean	invokeVelocimacro(String vmName, String logTag, String[] params, Context context, Writer writer) Invokes a currently registered Velocimacro with the params provided and places the rendered stream into the writer.
static boolean	mergeTemplate(String templateName, Context context, Writer writer) Deprecated. Use mergeTemplate( String templateName, String encoding, Context context, Writer writer )
static boolean	mergeTemplate(String templateName, String encoding, Context context, Writer writer) merges a template and puts the rendered stream into the writer
static boolean	resourceExists(String resourceName) Determines whether a resource is accessable via the currently configured resource loaders.
static void	setApplicationAttribute(Object key, Object value) Set the an ApplicationAttribue, which is an Object set by the application which is accessable from any component of the system that gets a RuntimeServices.
static void	setExtendedProperties(ExtendedProperties configuration) Set an entire configuration at once.
static void	setProperty(String key, Object value) Set a Velocity Runtime property.
static boolean	templateExists(String resourceName) Deprecated. Use resourceExists(String) instead.
static void	warn(Object message) Deprecated. Use getLog() and call warn() on it.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Velocity

public Velocity()

Method Detail

init

public static void init()
                 throws Exception

initialize the Velocity runtime engine, using the default properties of the Velocity distribution

Throws:

Exception - When an error during initialization occurs.

init

public static void init(String propsFilename)
                 throws Exception

initialize the Velocity runtime engine, using default properties plus the properties in the properties file passed in as the arg

Parameters:

propsFilename - file containing properties to use to initialize the Velocity runtime

Throws:

Exception - When an error during initialization occurs.

init

public static void init(Properties p)
                 throws Exception

initialize the Velocity runtime engine, using default properties plus the properties in the passed in java.util.Properties object

Parameters:

p - Properties object containing initialization properties

Throws:

Exception - When an error during initialization occurs.

setProperty

public static void setProperty(String key,
                               Object value)

Set a Velocity Runtime property.

Parameters:

key - The property key.

value - The property value.

addProperty

public static void addProperty(String key,
                               Object value)

Add a Velocity Runtime property.

Parameters:

key - The property key.

value - The property value.

clearProperty

public static void clearProperty(String key)

Clear a Velocity Runtime property.

Parameters:

key - of property to clear

setExtendedProperties

public static void setExtendedProperties(ExtendedProperties configuration)

Set an entire configuration at once. This is useful in cases where the parent application uses the ExtendedProperties class and the velocity configuration is a subset of the parent application's configuration.

Parameters:

configuration - A configuration object.

getProperty

public static Object getProperty(String key)

Get a Velocity Runtime property.

Parameters:

key - property to retrieve

Returns:

property value or null if the property not currently set

evaluate

public static boolean evaluate(Context context,
                               Writer out,
                               String logTag,
                               String instring)
                        throws ParseErrorException,
                               MethodInvocationException,
                               ResourceNotFoundException,
                               IOException

renders the input string using the context into the output writer. To be used when a template is dynamically constructed, or want to use Velocity as a token replacer.

Parameters:

context - context to use in rendering input string

out - Writer in which to render the output

logTag - string to be used as the template name for log messages in case of error

instring - input string containing the VTL to be rendered

Returns:

true if successful, false otherwise. If false, see Velocity runtime log

Throws:

ParseErrorException - The template could not be parsed.

MethodInvocationException - A method on a context object could not be invoked.

ResourceNotFoundException - A referenced resource could not be loaded.

IOException - While rendering to the writer, an I/O problem occured.

evaluate

public static boolean evaluate(Context context,
                               Writer writer,
                               String logTag,
                               InputStream instream)
                        throws ParseErrorException,
                               MethodInvocationException,
                               ResourceNotFoundException,
                               IOException

Deprecated. Use evaluate( Context context, Writer writer, String logTag, Reader reader )

Renders the input stream using the context into the output writer. To be used when a template is dynamically constructed, or want to use Velocity as a token replacer.

Parameters:

context - context to use in rendering input string

writer - Writer in which to render the output

logTag - string to be used as the template name for log messages in case of error

instream - input stream containing the VTL to be rendered

Returns:

true if successful, false otherwise. If false, see Velocity runtime log

Throws:

ParseErrorException - The template could not be parsed.

MethodInvocationException - A method on a context object could not be invoked.

ResourceNotFoundException - A referenced resource could not be loaded.

IOException - While loading a reference, an I/O problem occured.

evaluate

public static boolean evaluate(Context context,
                               Writer writer,
                               String logTag,
                               Reader reader)
                        throws ParseErrorException,
                               MethodInvocationException,
                               ResourceNotFoundException,
                               IOException

Renders the input reader using the context into the output writer. To be used when a template is dynamically constructed, or want to use Velocity as a token replacer.

Parameters:

context - context to use in rendering input string

writer - Writer in which to render the output

logTag - string to be used as the template name for log messages in case of error

reader - Reader containing the VTL to be rendered

Returns:

true if successful, false otherwise. If false, see Velocity runtime log

Throws:

ParseErrorException - The template could not be parsed.

MethodInvocationException - A method on a context object could not be invoked.

ResourceNotFoundException - A referenced resource could not be loaded.

IOException - While reading from the reader or rendering to the writer, an I/O problem occured.

Since:

Velocity v1.1

invokeVelocimacro

public static boolean invokeVelocimacro(String vmName,
                                        String logTag,
                                        String[] params,
                                        Context context,
                                        Writer writer)

Invokes a currently registered Velocimacro with the params provided and places the rendered stream into the writer.
Note : currently only accepts args to the VM if they are in the context.

Parameters:

vmName - name of Velocimacro to call

logTag - string to be used for template name in case of error. if null, the vmName will be used

params - keys for args used to invoke Velocimacro, in java format rather than VTL (eg "foo" or "bar" rather than "$foo" or "$bar")

context - Context object containing data/objects used for rendering.

writer - Writer for output stream

Returns:

true if Velocimacro exists and successfully invoked, false otherwise.

mergeTemplate

public static boolean mergeTemplate(String templateName,
                                    Context context,
                                    Writer writer)
                             throws ResourceNotFoundException,
                                    ParseErrorException,
                                    MethodInvocationException,
                                    Exception

Deprecated. Use mergeTemplate( String templateName, String encoding, Context context, Writer writer )

Merges a template and puts the rendered stream into the writer. The default encoding that Velocity uses to read template files is defined in the property input.encoding and defaults to ISO-8859-1.

Parameters:

templateName - name of template to be used in merge

context - filled context to be used in merge

writer - writer to write template into

Returns:

true if successful, false otherwise. Errors logged to velocity log.

Throws:

ParseErrorException - The template could not be parsed.

MethodInvocationException - A method on a context object could not be invoked.

ResourceNotFoundException - A referenced resource could not be loaded.

Exception - Any other exception.

mergeTemplate

public static boolean mergeTemplate(String templateName,
                                    String encoding,
                                    Context context,
                                    Writer writer)
                             throws ResourceNotFoundException,
                                    ParseErrorException,
                                    MethodInvocationException,
                                    Exception

merges a template and puts the rendered stream into the writer

Parameters:

templateName - name of template to be used in merge

encoding - encoding used in template

context - filled context to be used in merge

writer - writer to write template into

Returns:

true if successful, false otherwise. Errors logged to velocity log

Throws:

ParseErrorException - The template could not be parsed.

MethodInvocationException - A method on a context object could not be invoked.

ResourceNotFoundException - A referenced resource could not be loaded.

Exception - Any other exception.

Since:

Velocity v1.1

getTemplate

public static Template getTemplate(String name)
                            throws ResourceNotFoundException,
                                   ParseErrorException,
                                   Exception

Returns a Template from the Velocity resource management system.

Parameters:

name - The file name of the desired template.

Returns:

The template.

Throws:

ResourceNotFoundException - if template not found from any available source.

ParseErrorException - if template cannot be parsed due to syntax (or other) error.

Exception - if an error occurs in template initialization

getTemplate

public static Template getTemplate(String name,
                                   String encoding)
                            throws ResourceNotFoundException,
                                   ParseErrorException,
                                   Exception

Returns a Template from the Velocity resource management system.

Parameters:

name - The file name of the desired template.

encoding - The character encoding to use for the template.

Returns:

The template.

Throws:

ResourceNotFoundException - if template not found from any available source.

ParseErrorException - if template cannot be parsed due to syntax (or other) error.

Exception - if an error occurs in template initialization

Since:

Velocity v1.1

resourceExists

public static boolean resourceExists(String resourceName)

Determines whether a resource is accessable via the currently configured resource loaders. Resource is the generic description of templates, static content, etc.

Note that the current implementation will not change the state of the system in any real way - so this cannot be used to pre-load the resource cache, as the previous implementation did as a side-effect.

Parameters:

resourceName - The name of the resource to search for.

Returns:

Whether the resource was located.

getLog

public static Log getLog()

Returns a convenient Log instance that wraps the current LogChute. Use this to log error messages. It has the usual methods.

Returns:

A convenience Log instance that wraps the current LogChute.

Since:

1.5

warn

public static void warn(Object message)

Deprecated. Use getLog() and call warn() on it.

Parameters:

message - The message to log.

See Also:

Log.warn(Object)

info

public static void info(Object message)

Deprecated. Use getLog() and call info() on it.

Parameters:

message - The message to log.

See Also:

Log.info(Object)

error

public static void error(Object message)

Deprecated. Use getLog() and call error() on it.

Parameters:

message - The message to log.

See Also:

Log.error(Object)

debug

public static void debug(Object message)

Deprecated. Use getLog() and call debug() on it.

Parameters:

message - The message to log.

See Also:

Log.debug(Object)

setApplicationAttribute

public static void setApplicationAttribute(Object key,
                                           Object value)

Set the an ApplicationAttribue, which is an Object set by the application which is accessable from any component of the system that gets a RuntimeServices. This allows communication between the application environment and custom pluggable components of the Velocity engine, such as loaders and loggers.

Note that there is no enfocement or rules for the key used - it is up to the application developer. However, to help make the intermixing of components possible, using the target Class name (e.g. com.foo.bar ) as the key might help avoid collision.

Parameters:

key - object 'name' under which the object is stored

value - object to store under this key

templateExists

public static boolean templateExists(String resourceName)

Deprecated. Use resourceExists(String) instead.

Parameters:

resourceName - Name of the Template to check.

Returns:

True if the template exists.

See Also:

resourceExists(String)