Package org.apache.velocity.app

Class Velocity

  • All Implemented Interfaces:
    DeprecatedRuntimeConstants, 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:
    $Id$
    Author:
    Geir Magnusson Jr., Christoph Reck, Jason van Zyl

    • Constructor Detail

      • Velocity

        public Velocity()

    • Method Detail

      • init

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

      • reset

        public static void reset()
        Resets the instance, so Velocity can be re-initialized again.
        Since:
        2.0.0

      • init

        public 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
        Parameters:
        propsFilename - file containing properties to use to initialize the Velocity runtime

      • init

        public static void init​(Properties p)
        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

      • 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

      • setProperties

        public static void setProperties​(Properties configuration)
        Set an entire configuration at once.
        Parameters:
        configuration - A configuration object.
        Since:
        2.0

      • 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
        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.

      • evaluate

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

      • resourceExists

        public static boolean resourceExists​(String resourceName)

        Determines whether a resource is accessible 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 org.slf4j.Logger getLog()
        Returns the current logger.
        Returns:
        A convenience Logger instance.
        Since:
        1.5

      • setApplicationAttribute

        public static void setApplicationAttribute​(Object key,
                                           Object value)

        Set the an ApplicationAttribue, which is an Object set by the application which is 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 loaders and loggers.

        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

      • removeDirective

        public void removeDirective​(String name)
        Remove a directive.
        Parameters:
        name - name of the directive.

      • loadDirective

        public void loadDirective​(String directiveClass)
        Instantiates and loads the directive with some basic checks.
        Parameters:
        directiveClass - classname of directive to load