org.apache.velocity.app

Class Velocity

Implemented Interfaces:
RuntimeConstants

public class Velocity
extends java.lang.Object
implements RuntimeConstants

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

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,v 1.27 2002/01/03 12:41:19 geirm Exp $

Authors:
Geir Magnusson Jr.
Christoph Reck
Jason van Zyl

Nested Class Summary

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

COUNTER_INITIAL_VALUE, COUNTER_NAME, DEBUG_PREFIX, DEFAULT_RUNTIME_DIRECTIVES, DEFAULT_RUNTIME_PROPERTIES, ENCODING_DEFAULT, ERRORMSG_END, ERRORMSG_START, ERROR_PREFIX, FILE_RESOURCE_LOADER_CACHE, FILE_RESOURCE_LOADER_PATH, INFO_PREFIX, INPUT_ENCODING, INTERPOLATE_STRINGLITERALS, LOGSYSTEM_LOG4J_EMAIL_BUFFER_SIZE, LOGSYSTEM_LOG4J_EMAIL_FROM, LOGSYSTEM_LOG4J_EMAIL_SERVER, LOGSYSTEM_LOG4J_EMAIL_SUBJECT, LOGSYSTEM_LOG4J_EMAIL_TO, LOGSYSTEM_LOG4J_FILE_BACKUPS, LOGSYSTEM_LOG4J_FILE_SIZE, LOGSYSTEM_LOG4J_PATTERN, LOGSYSTEM_LOG4J_REMOTE_HOST, LOGSYSTEM_LOG4J_REMOTE_PORT, LOGSYSTEM_LOG4J_SYSLOGD_FACILITY, LOGSYSTEM_LOG4J_SYSLOGD_HOST, NUMBER_OF_PARSERS, OUTPUT_ENCODING, PARSER_POOL_SIZE, PARSE_DIRECTIVE_MAXDEPTH, RESOURCE_LOADER, RESOURCE_MANAGER_CACHE_CLASS, RESOURCE_MANAGER_CLASS, 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, UNKNOWN_PREFIX, VM_CONTEXT_LOCALSCOPE, VM_LIBRARY, VM_LIBRARY_AUTORELOAD, VM_MESSAGES_ON, VM_PERM_ALLOW_INLINE, VM_PERM_ALLOW_INLINE_REPLACE_GLOBAL, VM_PERM_INLINE_LOCAL, WARN_PREFIX

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)
Log a debug message.
static void
error(Object message)
Log an error message.
static boolean
evaluate(Context context, Writer writer, String logTag, InputStream instream)
Deprecated. Use
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 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)
Log an info message.
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, params[] , Context context, Writer writer)
Invokes a currently registered Velocimacro with the parms provided and places the rendered stream into the 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
mergeTemplate(String templateName, Context context, Writer writer)
Deprecated. Use
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
setConfiguration(Configuration configuration)
Deprecated. Use
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 templateName)
Determines if a template is accessable via the currently configured resource loaders.
static void
warn(Object message)
Log a warning message.

Method Details

addProperty

public static void addProperty(String key,
                               Object value)
Add a Velocity Runtime property.

Parameters:


clearProperty

public static void clearProperty(String key)
Clear a Velocity Runtime property.

Parameters:
key - of property to clear


debug

public static void debug(Object message)
Log a debug message.

Parameters:


error

public static void error(Object message)
Log an error message.

Parameters:


evaluate

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

Deprecated. Use

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

Parameters:
context - context to use in rendering input string
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


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
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

Since:
Velocity v1.1


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


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


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.


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.

Since:
Velocity v1.1


info

public static void info(Object message)
Log an info message.

Parameters:


init

public static void init()
            throws Exception
initialize the Velocity runtime engine, using the default properties of the Velocity distribution


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 - Proprties object containing initialization properties


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


invokeVelocimacro

public static boolean invokeVelocimacro(String vmName,
                                        String logTag,
                                        params[] ,
                                        Context context,
                                        Writer writer)
Invokes a currently registered Velocimacro with the parms 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
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,
                                    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

Since:
Velocity v1.1


mergeTemplate

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

Deprecated. Use

merges a template and puts the rendered stream into the writer mergeTemplate( String templateName, String encoding, Context context, Writer writer )

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.


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


setConfiguration

public static void setConfiguration(Configuration configuration)

Deprecated. Use

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

Parameters:


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:


setProperty

public static void setProperty(String key,
                               Object value)
Set a Velocity Runtime property.

Parameters:


templateExists

public static boolean templateExists(String templateName)
Determines if a template is accessable via the currently configured resource loaders.

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.

The previous implementation exhibited extreme lazyness and sloth, and the author has been flogged.

Parameters:
templateName - name of the temlpate to search for

Returns:
true if found, false otherwise


warn

public static void warn(Object message)
Log a warning message.

Parameters:


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