Package org.apache.velocity.app

Class VelocityEngine

java.lang.Object
org.apache.velocity.app.VelocityEngine
All Implemented Interfaces:
DeprecatedRuntimeConstants, 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:
$Id$

  • Constructor Details

    • VelocityEngine

      public VelocityEngine()
      Init-less CTOR

    • VelocityEngine

      public VelocityEngine(String propsFilename)
      Construct a VelocityEngine with the initial properties defined in the file propsFilename
      Parameters:
      propsFilename - properties filename

    • VelocityEngine

      public VelocityEngine(Properties p)
      Construct a VelocityEngine instance with the specified initial properties.
      Parameters:
      p - properties

  • Method Details

    • init

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

    • reset

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

    • init

      public 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 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 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

    • setProperties

      public void setProperties(Properties configuration)
      Set an entire configuration at once from a Properties configuration
      Parameters:
      configuration -
      Since:
      2.0

    • setProperties

      public void setProperties(String propsFilename)
      Set an entire configuration at once from a named properties file
      Parameters:
      propsFilename - properties filename
      Since:
      2.1

    • 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
      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, 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 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 boolean mergeTemplate(String templateName, String encoding, Context context, Writer writer) throws ResourceNotFoundException, ParseErrorException, MethodInvocationException
      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
      Since:
      Velocity v1.1

    • getTemplate

      public Template getTemplate(String name) throws ResourceNotFoundException, ParseErrorException
      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 Template getTemplate(String name, 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(String resourceName)
      Determines if a resource is accessible 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 laziness 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

    • getLog

      public org.slf4j.Logger getLog()
      Returns the current slf4j logger. Its namespace defaults to org.apache.velocity if it hasn't been configured using the property runtime.log.name or the property runtime.log.instance.
      Returns:
      A Logger object.
      Since:
      1.5

    • 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 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

    • 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 Loggers.

      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(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