org.apache.velocity.app
Class VelocityEngine

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

All Implemented Interfaces:

RuntimeConstants

public class VelocityEngine
extends Object
implements RuntimeConstants

This class provides a separate new-able instance of the Velocity template engine. The alternative model for use is using the Velocity class which employs the singleton model.

Velocity will call the parameter-less init() at the first use of this class if the init() wasn't explicitly called. While this will ensure that Velocity functions, it probably won't function in the way you intend, so it is strongly recommended that you call an init() method yourself if you use the default constructor.

Version:

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

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

VelocityEngine()
Init-less CTOR

VelocityEngine(Properties p)
CTOR that invokes an init(String), initializing the engine using the Properties specified

VelocityEngine(String propsFilename)
CTOR that invokes an init(String), initializing the engine using the properties file specified

Method Summary

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

VelocityEngine

public VelocityEngine()

Init-less CTOR

VelocityEngine

public VelocityEngine(String propsFilename)
               throws Exception

CTOR that invokes an init(String), initializing the engine using the properties file specified

Parameters:

propsFilename - name of properties file to init with

Throws:

Exception

Since:

1.5

VelocityEngine

public VelocityEngine(Properties p)
               throws Exception

CTOR that invokes an init(String), initializing the engine using the Properties specified

Parameters:

p - name of properties to init with

Throws:

Exception

Since:

1.5

Method Detail

init

public void init()
          throws Exception

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

Throws:

Exception

init

public 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

init

public 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

Throws:

Exception

setProperty

public void setProperty(String key,
                        Object value)

Set a Velocity Runtime property.

Parameters:

key -

value -

addProperty

public void addProperty(String key,
                        Object value)

Add a Velocity Runtime property.

Parameters:

key -

value -

clearProperty

public void clearProperty(String key)

Clear a Velocity Runtime property.

Parameters:

key - of property to clear

setExtendedProperties

public 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 -

getProperty

public 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 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 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

MethodInvocationException

ResourceNotFoundException

IOException

evaluate

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

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.

Throws:

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

Exception

mergeTemplate

public 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:

ResourceNotFoundException

ParseErrorException

MethodInvocationException

Exception

mergeTemplate

public 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:

ResourceNotFoundException

ParseErrorException

MethodInvocationException

Exception

Since:

Velocity v1.1

getTemplate

public 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 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 boolean resourceExists(String resourceName)

Determines if a resource 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:

resourceName - name of the resource to search for

Returns:

true if found, false otherwise

Since:

1.5

templateExists

public boolean templateExists(String resourceName)

Deprecated. Use resourceExists(String) instead.

Parameters:

resourceName -

Returns:

True if the template exists.

See Also:

resourceExists(String)

getLog

public Log getLog()

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

Returns:

A log object.

Since:

1.5

warn

public void warn(Object message)

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

Parameters:

message -

info

public void info(Object message)

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

Parameters:

message -

error

public void error(Object message)

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

Parameters:

message -

debug

public void debug(Object message)

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

Parameters:

message -

setApplicationAttribute

public void setApplicationAttribute(Object key,
                                    Object value)

Sets an application attribute (which can be any Object) that will be accessible 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 ResourceLoaders and LogChutes.

Note that there is no enforcement 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

getApplicationAttribute

public Object getApplicationAttribute(Object key)

Return an application attribute (which can be any Object) that was set by the application in order to be accessible 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 ResourceLoaders and LogChutes.

Parameters:

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

Returns:

value object to store under this key

Since:

1.5