com.continuent.tungsten.replicator.filter
Class JavaScriptFilter

java.lang.Object
  com.continuent.tungsten.replicator.filter.JavaScriptFilter

All Implemented Interfaces:

Filter, FilterManualProperties, ReplicatorPlugin

public class JavaScriptFilter
extends java.lang.Object
implements FilterManualProperties

This filter allows to develop JavaScript filters without coding any Java at all.

User's script will be precompiled once and then called on every filtered event.

Script must define the following function:
function filter(event) - called on every filtered ReplDBMSEvent.

filter(event) function's return value is handled as follows:
a. null and ReplDBMSEvent - passed through to the JavaScriptFilter's caller,
b. Undefined (no return statement in the JS) - ignored,
c. Everything else - logged into INFO stream.

Further functions may be defined, but are optional:
function prepare() - called when this filter is being prepared.
function release() - called when this filter is being released.

Any of these functions are free to return a value. If they do, value is logged into trep.log INFO stream.

Also there are the following variables exported via JavaScript reflection for user's usage:
properties - TungstenProperties of the current replicator instance;
filterProperties - TungstenProperties subset with the current filter's properties (eg. "script");
logger - this classes Logger. Eg. of usage: logger.info("I'm a script!");
thread - current Thread. Eg. of usage: thread.sleep(1000);

Note: if you wish to call more than one JS file, use multiple instances of this filter with different names defined in replicator.properties

Author:

Linas Virbalas

Constructor Summary

JavaScriptFilter()

Method Summary

void	configure(PluginContext context) Complete plug-in configuration.
ReplDBMSEvent	filter(ReplDBMSEvent event) Calls filter(event) function in user's script.
void	prepare(PluginContext context) Reads and compiles user's script.
void	release(PluginContext context) Calls script's release() function if it exists.
void	setConfigPrefix(java.lang.String configPrefix) Set filter's configuration prefix.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JavaScriptFilter

public JavaScriptFilter()

Method Detail

setConfigPrefix

public void setConfigPrefix(java.lang.String configPrefix)

Set filter's configuration prefix. This is important in order for the filter to be able to know where its properties are in the configuration file.
Eg. of how filter's properties could be read:
TungstenProperties filterProperties = properties.subset(configPrefix + ".", true);

Specified by:

setConfigPrefix in interface FilterManualProperties

Parameters:

configPrefix - Configuration prefix.

See Also:

FilterManualProperties.setConfigPrefix(java.lang.String)

filter

public ReplDBMSEvent filter(ReplDBMSEvent event)
                     throws ReplicatorException,
                            java.lang.InterruptedException

Calls filter(event) function in user's script. Blocks until it returns. Filter the event. Filters may transform the event or return null if the event should be discarded. Filters must be prepared to be interrupted, which mechanism is used to cancel processing.

Specified by:

filter in interface Filter

Parameters:

event - An event to be filtered

Returns:

Filtered ReplDBMSEvent or null

Throws:

ReplicatorException - Thrown if there is a processing error

java.lang.InterruptedException - Must be thrown if the filter is interrupted or the replicator may hang

See Also:

Filter.filter(com.continuent.tungsten.replicator.event.ReplDBMSEvent)

configure

public void configure(PluginContext context)
               throws ReplicatorException

Complete plug-in configuration. This is called after setters are invoked at the time that the replicator goes through configuration.

Specified by:

configure in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if configuration is incomplete or fails

See Also:

ReplicatorPlugin.configure(com.continuent.tungsten.replicator.plugin.PluginContext)

prepare

public void prepare(PluginContext context)
             throws ReplicatorException

Reads and compiles user's script. Initializes function reflection objects. Calls script's prepare() function if it exists. Prepare plug-in for use. This method is assumed to allocate all required resources. It is called before the plug-in performs any operations.

Specified by:

prepare in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if resource allocation fails

See Also:

ReplicatorPlugin.prepare(com.continuent.tungsten.replicator.plugin.PluginContext)

release

public void release(PluginContext context)
             throws ReplicatorException

Calls script's release() function if it exists. Closes JavaScript context. Release all resources used by plug-in. This is called before the plug-in is deallocated.

Specified by:

release in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if resource deallocation fails

See Also:

ReplicatorPlugin.release(com.continuent.tungsten.replicator.plugin.PluginContext)