task.java

java ant的源码！非常值得看的源码

     * @param length the amount of data to read.
     *
     * @return the number of bytes read.
     *
     * @exception IOException if the data cannot be read.
     * @since Ant 1.6
     */
    protected int handleInput(byte[] buffer, int offset, int length)
        throws IOException {
        return getProject().defaultInput(buffer, offset, length);
    }

    /**
     * Handles an error output by logging it with the WARN priority.
     *
     * @param output The error output to log. Should not be <code>null</code>.
     */
    protected void handleErrorOutput(String output) {
        log(output, Project.MSG_WARN);
    }

    /**
     * Handles an error line by logging it with the WARN priority.
     *
     * @param output The error output to log. Should not be <code>null</code>.
     *
     * @since Ant 1.5.2
     */
    protected void handleErrorFlush(String output) {
        handleErrorOutput(output);
    }

    /**
     * Logs a message with the default (INFO) priority.
     *
     * @param msg The message to be logged. Should not be <code>null</code>.
     */
    public void log(String msg) {
        log(msg, Project.MSG_INFO);
    }

    /**
     * Logs a message with the given priority. This delegates
     * the actual logging to the project.
     *
     * @param msg The message to be logged. Should not be <code>null</code>.
     * @param msgLevel The message priority at which this message is to
     *                 be logged.
     */
    public void log(String msg, int msgLevel) {
        if (getProject() != null) {
            getProject().log(this, msg, msgLevel);
        } else {
            super.log(msg, msgLevel);
        }
    }

    /**
     * Logs a message with the given priority. This delegates
     * the actual logging to the project.
     *
     * @param t The exception to be logged. Should not be <code>null</code>.
     * @param msgLevel The message priority at which this message is to
     *                 be logged.
     * @since 1.7
     */
    public void log(Throwable t, int msgLevel) {
        if (t != null) {
            log(t.getMessage(), t, msgLevel);
        }
    }

    /**
     * Logs a message with the given priority. This delegates
     * the actual logging to the project.
     *
     * @param msg The message to be logged. Should not be <code>null</code>.
     * @param t The exception to be logged. May be <code>null</code>.
     * @param msgLevel The message priority at which this message is to
     *                 be logged.
     * @since 1.7
     */
    public void log(String msg, Throwable t, int msgLevel) {
        if (getProject() != null) {
            getProject().log(this, msg, t, msgLevel);
        } else {
            super.log(msg, msgLevel);
        }
    }

    /**
     * Performs this task if it's still valid, or gets a replacement
     * version and performs that otherwise.
     *
     * Performing a task consists of firing a task started event,
     * configuring the task, executing it, and then firing task finished
     * event. If a runtime exception is thrown, the task finished event
     * is still fired, but with the exception as the cause.
     */
    public final void perform() {
        if (!invalid) {
            getProject().fireTaskStarted(this);
            Throwable reason = null;
            try {
                maybeConfigure();
                DispatchUtils.execute(this);
            } catch (BuildException ex) {
                if (ex.getLocation() == Location.UNKNOWN_LOCATION) {
                    ex.setLocation(getLocation());
                }
                reason = ex;
                throw ex;
            } catch (Exception ex) {
                reason = ex;
                BuildException be = new BuildException(ex);
                be.setLocation(getLocation());
                throw be;
            } catch (Error ex) {
                reason = ex;
                throw ex;
            } finally {
                getProject().fireTaskFinished(this, reason);
            }
        } else {
            UnknownElement ue = getReplacement();
            Task task = ue.getTask();
            task.perform();
        }
    }

    /**
     * Marks this task as invalid. Any further use of this task
     * will go through a replacement with the updated definition.
     */
    final void markInvalid() {
        invalid = true;
    }

    /**
     * Has this task been marked invalid?
     *
     * @return true if this task is no longer valid. A new task should be
     * configured in this case.
     *
     * @since Ant 1.5
     */
    protected final boolean isInvalid() {
        return invalid;
    }

    /**
     * Replacement element used if this task is invalidated.
     */
    private UnknownElement replacement;

    /**
     * Creates an UnknownElement that can be used to replace this task.
     * Once this has been created once, it is cached and returned by
     * future calls.
     *
     * @return the UnknownElement instance for the new definition of this task.
     */
    private UnknownElement getReplacement() {
        if (replacement == null) {
            replacement = new UnknownElement(taskType);
            replacement.setProject(getProject());
            replacement.setTaskType(taskType);
            replacement.setTaskName(taskName);
            replacement.setLocation(location);
            replacement.setOwningTarget(target);
            replacement.setRuntimeConfigurableWrapper(wrapper);
            wrapper.setProxy(replacement);
            replaceChildren(wrapper, replacement);
            target.replaceChild(this, replacement);
            replacement.maybeConfigure();
        }
        return replacement;
    }

    /**
     * Recursively adds an UnknownElement instance for each child
     * element of replacement.
     *
     * @since Ant 1.5.1
     */
    private void replaceChildren(RuntimeConfigurable wrapper,
                                 UnknownElement parentElement) {
        Enumeration e = wrapper.getChildren();
        while (e.hasMoreElements()) {
            RuntimeConfigurable childWrapper =
                (RuntimeConfigurable) e.nextElement();
            UnknownElement childElement =
                new UnknownElement(childWrapper.getElementTag());
            parentElement.addChild(childElement);
            childElement.setProject(getProject());
            childElement.setRuntimeConfigurableWrapper(childWrapper);
            childWrapper.setProxy(childElement);
            replaceChildren(childWrapper, childElement);
        }
    }

    /**
     * Return the type of task.
     *
     * @return the type of task.
     */
    public String getTaskType() {
        return taskType;
    }

    /**
     * Return the runtime configurable structure for this task.
     *
     * @return the runtime structure for this task.
     */
    protected RuntimeConfigurable getWrapper() {
        return wrapper;
    }

    /**
     * Bind a task to another; use this when configuring a newly created
     * task to do work on behalf of another.
     * Project, OwningTarget, TaskName, Location and Description are all copied
     *
     * Important: this method does not call {@link Task#init()}.
     * If you are creating a task to delegate work to, call {@link Task#init()}
     * to initialize it.
     *
     * @param owner owning target
     * @since Ant1.7
     */
    public final void bindToOwner(Task owner) {
        setProject(owner.getProject());
        setOwningTarget(owner.getOwningTarget());
        setTaskName(owner.getTaskName());
        setDescription(owner.getDescription());
        setLocation(owner.getLocation());
        setTaskType(owner.getTaskType());
    }
}