Class VelocityEngine

  • All Implemented Interfaces:
    RuntimeConstants

    public class VelocityEngine
    extends java.lang.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 894920 2009-12-31 18:35:25Z nbubna $
    • Constructor Detail

      • VelocityEngine

        public VelocityEngine()
        Init-less CTOR
      • VelocityEngine

        public VelocityEngine​(java.lang.String propsFilename)
        Construct a VelocityEngine with the initial properties defined in the file propsFilename
      • VelocityEngine

        public VelocityEngine​(java.util.Properties p)
        Construct a VelocityEngine instance with the specified initial properties.
    • Method Detail

      • init

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

        public void init​(java.lang.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 void init​(java.util.Properties p)
        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
      • setProperty

        public void setProperty​(java.lang.String key,
                                java.lang.Object value)
        Set a Velocity Runtime property.
        Parameters:
        key -
        value -
      • addProperty

        public void addProperty​(java.lang.String key,
                                java.lang.Object value)
        Add a Velocity Runtime property.
        Parameters:
        key -
        value -
      • clearProperty

        public void clearProperty​(java.lang.String key)
        Clear a Velocity Runtime property.
        Parameters:
        key - of property to clear
      • setExtendedProperties

        public void setExtendedProperties​(org.apache.commons.collections.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 java.lang.Object getProperty​(java.lang.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,
                                java.io.Writer out,
                                java.lang.String logTag,
                                java.lang.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 boolean evaluate​(Context context,
                                java.io.Writer writer,
                                java.lang.String logTag,
                                java.io.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 boolean invokeVelocimacro​(java.lang.String vmName,
                                         java.lang.String logTag,
                                         java.lang.String[] params,
                                         Context context,
                                         java.io.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.
      • getTemplate

        public Template getTemplate​(java.lang.String name,
                                    java.lang.String encoding)
                             throws ResourceNotFoundException,
                                    ParseErrorException
        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
      • resourceExists

        public boolean resourceExists​(java.lang.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​(java.lang.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​(java.lang.Object message)
        Deprecated.
        Use getLog() and call warn() on it.
        Parameters:
        message -
      • info

        public void info​(java.lang.Object message)
        Deprecated.
        Use getLog() and call warn() on it.
        Parameters:
        message -
      • error

        public void error​(java.lang.Object message)
        Deprecated.
        Use getLog() and call warn() on it.
        Parameters:
        message -
      • debug

        public void debug​(java.lang.Object message)
        Deprecated.
        Use getLog() and call warn() on it.
        Parameters:
        message -
      • setApplicationAttribute

        public void setApplicationAttribute​(java.lang.Object key,
                                            java.lang.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 java.lang.Object getApplicationAttribute​(java.lang.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
      • removeDirective

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

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