https://tomcat.apache.org/: Tomcat Servlet Engine Core Classes and Standard implementations 
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 *      http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.catalina.core;


import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import javax.management.ObjectName;

import org.apache.catalina.Contained;
import org.apache.catalina.Container;
import org.apache.catalina.JmxEnabled;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.Pipeline;
import org.apache.catalina.Valve;
import org.apache.catalina.util.LifecycleBase;
import org.apache.catalina.util.ToStringUtil;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.res.StringManager;



Standard implementation of a processing Pipeline that will invoke
a series of Valves that have been configured to be called in order.  This
implementation can be used for any type of Container.
IMPLEMENTATION WARNING - This implementation assumes that no
calls to addValve() or removeValve are allowed
while a request is currently being processed.  Otherwise, the mechanism
by which per-thread state is maintained will need to be modified.

Author:Craig R. McClanahan
/**
 * Standard implementation of a processing <b>Pipeline</b> that will invoke
 * a series of Valves that have been configured to be called in order.  This
 * implementation can be used for any type of Container.
 *
 * <b>IMPLEMENTATION WARNING</b> - This implementation assumes that no
 * calls to <code>addValve()</code> or <code>removeValve</code> are allowed
 * while a request is currently being processed.  Otherwise, the mechanism
 * by which per-thread state is maintained will need to be modified.
 *
 * @author Craig R. McClanahan
 */

public class StandardPipeline extends LifecycleBase implements Pipeline {

    private static final Log log = LogFactory.getLog(StandardPipeline.class);
    private static final StringManager sm = StringManager.getManager(Constants.Package);

    // ----------------------------------------------------------- Constructors


    
Construct a new StandardPipeline instance with no associated Container.

/**
     * Construct a new StandardPipeline instance with no associated Container.
     */
    public StandardPipeline() {

        this(null);

    }


    
Construct a new StandardPipeline instance that is associated with the
specified Container.

Params:
  • container – The container we should be associated with
/**
     * Construct a new StandardPipeline instance that is associated with the
     * specified Container.
     *
     * @param container The container we should be associated with
     */
    public StandardPipeline(Container container) {

        super();
        setContainer(container);

    }


    // ----------------------------------------------------- Instance Variables


    
The basic Valve (if any) associated with this Pipeline.

/**
     * The basic Valve (if any) associated with this Pipeline.
     */
    protected Valve basic = null;


    
The Container with which this Pipeline is associated.

/**
     * The Container with which this Pipeline is associated.
     */
    protected Container container = null;


    
The first valve associated with this Pipeline.

/**
     * The first valve associated with this Pipeline.
     */
    protected Valve first = null;


    // --------------------------------------------------------- Public Methods

    @Override
    public boolean isAsyncSupported() {
        Valve valve = (first!=null)?first:basic;
        boolean supported = true;
        while (supported && valve!=null) {
            supported = supported & valve.isAsyncSupported();
            valve = valve.getNext();
        }
        return supported;
    }


    @Override
    public void findNonAsyncValves(Set<String> result) {
        Valve valve = (first!=null) ? first : basic;
        while (valve != null) {
            if (!valve.isAsyncSupported()) {
                result.add(valve.getClass().getName());
            }
            valve = valve.getNext();
        }
    }


    // ------------------------------------------------------ Contained Methods

    
Return the Container with which this Pipeline is associated.

/**
     * Return the Container with which this Pipeline is associated.
     */
    @Override
    public Container getContainer() {
        return this.container;
    }


    
Set the Container with which this Pipeline is associated.

Params:
  • container – The new associated container
/**
     * Set the Container with which this Pipeline is associated.
     *
     * @param container The new associated container
     */
    @Override
    public void setContainer(Container container) {
        this.container = container;
    }


    @Override
    protected void initInternal() {
        // NOOP
    }


    
Start Valves) in this pipeline and implement the requirements of LifecycleBase.startInternal(). 
Throws:
  • LifecycleException – if this component detects a fatal error
 that prevents this component from being used
/**
     * Start {@link Valve}s) in this pipeline and implement the requirements
     * of {@link LifecycleBase#startInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    @Override
    protected synchronized void startInternal() throws LifecycleException {

        // Start the Valves in our pipeline (including the basic), if any
        Valve current = first;
        if (current == null) {
            current = basic;
        }
        while (current != null) {
            if (current instanceof Lifecycle)
                ((Lifecycle) current).start();
            current = current.getNext();
        }

        setState(LifecycleState.STARTING);
    }


    
Stop Valves) in this pipeline and implement the requirements of LifecycleBase.stopInternal(). 
Throws:
  • LifecycleException – if this component detects a fatal error
 that prevents this component from being used
/**
     * Stop {@link Valve}s) in this pipeline and implement the requirements
     * of {@link LifecycleBase#stopInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    @Override
    protected synchronized void stopInternal() throws LifecycleException {

        setState(LifecycleState.STOPPING);

        // Stop the Valves in our pipeline (including the basic), if any
        Valve current = first;
        if (current == null) {
            current = basic;
        }
        while (current != null) {
            if (current instanceof Lifecycle)
                ((Lifecycle) current).stop();
            current = current.getNext();
        }
    }


    @Override
    protected void destroyInternal() {
        Valve[] valves = getValves();
        for (Valve valve : valves) {
            removeValve(valve);
        }
    }


    
Return a String representation of this component.

/**
     * Return a String representation of this component.
     */
    @Override
    public String toString() {
        return ToStringUtil.toString(this);
    }


    // ------------------------------------------------------- Pipeline Methods


    
Return the Valve instance that has been distinguished as the basic
Valve for this Pipeline (if any).

/**
     * <p>Return the Valve instance that has been distinguished as the basic
     * Valve for this Pipeline (if any).
     */
    @Override
    public Valve getBasic() {
        return this.basic;
    }


    
Set the Valve instance that has been distinguished as the basic
Valve for this Pipeline (if any).  Prior to setting the basic Valve,
the Valve's setContainer() will be called, if it
implements Contained, with the owning Container as an
argument.  The method may throw an IllegalArgumentException
if this Valve chooses not to be associated with this Container, or
IllegalStateException if it is already associated with
a different Container.


Params:
  • valve – Valve to be distinguished as the basic Valve
/**
     * <p>Set the Valve instance that has been distinguished as the basic
     * Valve for this Pipeline (if any).  Prior to setting the basic Valve,
     * the Valve's <code>setContainer()</code> will be called, if it
     * implements <code>Contained</code>, with the owning Container as an
     * argument.  The method may throw an <code>IllegalArgumentException</code>
     * if this Valve chooses not to be associated with this Container, or
     * <code>IllegalStateException</code> if it is already associated with
     * a different Container.</p>
     *
     * @param valve Valve to be distinguished as the basic Valve
     */
    @Override
    public void setBasic(Valve valve) {

        // Change components if necessary
        Valve oldBasic = this.basic;
        if (oldBasic == valve)
            return;

        // Stop the old component if necessary
        if (oldBasic != null) {
            if (getState().isAvailable() && (oldBasic instanceof Lifecycle)) {
                try {
                    ((Lifecycle) oldBasic).stop();
                } catch (LifecycleException e) {
                    log.error(sm.getString("standardPipeline.basic.stop"), e);
                }
            }
            if (oldBasic instanceof Contained) {
                try {
                    ((Contained) oldBasic).setContainer(null);
                } catch (Throwable t) {
                    ExceptionUtils.handleThrowable(t);
                }
            }
        }

        // Start the new component if necessary
        if (valve == null)
            return;
        if (valve instanceof Contained) {
            ((Contained) valve).setContainer(this.container);
        }
        if (getState().isAvailable() && valve instanceof Lifecycle) {
            try {
                ((Lifecycle) valve).start();
            } catch (LifecycleException e) {
                log.error(sm.getString("standardPipeline.basic.start"), e);
                return;
            }
        }

        // Update the pipeline
        Valve current = first;
        while (current != null) {
            if (current.getNext() == oldBasic) {
                current.setNext(valve);
                break;
            }
            current = current.getNext();
        }

        this.basic = valve;

    }


    
Add a new Valve to the end of the pipeline associated with this
Container.  Prior to adding the Valve, the Valve's
setContainer() method will be called, if it implements
Contained, with the owning Container as an argument.
The method may throw an
IllegalArgumentException if this Valve chooses not to
be associated with this Container, or IllegalStateException
if it is already associated with a different Container.


Params:
  • valve – Valve to be added
Throws:
/**
     * <p>Add a new Valve to the end of the pipeline associated with this
     * Container.  Prior to adding the Valve, the Valve's
     * <code>setContainer()</code> method will be called, if it implements
     * <code>Contained</code>, with the owning Container as an argument.
     * The method may throw an
     * <code>IllegalArgumentException</code> if this Valve chooses not to
     * be associated with this Container, or <code>IllegalStateException</code>
     * if it is already associated with a different Container.</p>
     *
     * @param valve Valve to be added
     *
     * @exception IllegalArgumentException if this Container refused to
     *  accept the specified Valve
     * @exception IllegalArgumentException if the specified Valve refuses to be
     *  associated with this Container
     * @exception IllegalStateException if the specified Valve is already
     *  associated with a different Container
     */
    @Override
    public void addValve(Valve valve) {

        // Validate that we can add this Valve
        if (valve instanceof Contained)
            ((Contained) valve).setContainer(this.container);

        // Start the new component if necessary
        if (getState().isAvailable()) {
            if (valve instanceof Lifecycle) {
                try {
                    ((Lifecycle) valve).start();
                } catch (LifecycleException e) {
                    log.error(sm.getString("standardPipeline.valve.start"), e);
                }
            }
        }

        // Add this Valve to the set associated with this Pipeline
        if (first == null) {
            first = valve;
            valve.setNext(basic);
        } else {
            Valve current = first;
            while (current != null) {
                if (current.getNext() == basic) {
                    current.setNext(valve);
                    valve.setNext(basic);
                    break;
                }
                current = current.getNext();
            }
        }

        container.fireContainerEvent(Container.ADD_VALVE_EVENT, valve);
    }


    
Return the set of Valves in the pipeline associated with this
Container, including the basic Valve (if any).  If there are no
such Valves, a zero-length array is returned.

/**
     * Return the set of Valves in the pipeline associated with this
     * Container, including the basic Valve (if any).  If there are no
     * such Valves, a zero-length array is returned.
     */
    @Override
    public Valve[] getValves() {

        List<Valve> valveList = new ArrayList<>();
        Valve current = first;
        if (current == null) {
            current = basic;
        }
        while (current != null) {
            valveList.add(current);
            current = current.getNext();
        }

        return valveList.toArray(new Valve[0]);

    }

    public ObjectName[] getValveObjectNames() {

        List<ObjectName> valveList = new ArrayList<>();
        Valve current = first;
        if (current == null) {
            current = basic;
        }
        while (current != null) {
            if (current instanceof JmxEnabled) {
                valveList.add(((JmxEnabled) current).getObjectName());
            }
            current = current.getNext();
        }

        return valveList.toArray(new ObjectName[0]);

    }

    
Remove the specified Valve from the pipeline associated with this
Container, if it is found; otherwise, do nothing.  If the Valve is
found and removed, the Valve's setContainer(null) method
will be called if it implements Contained.

Params:
  • valve – Valve to be removed
/**
     * Remove the specified Valve from the pipeline associated with this
     * Container, if it is found; otherwise, do nothing.  If the Valve is
     * found and removed, the Valve's <code>setContainer(null)</code> method
     * will be called if it implements <code>Contained</code>.
     *
     * @param valve Valve to be removed
     */
    @Override
    public void removeValve(Valve valve) {

        Valve current;
        if(first == valve) {
            first = first.getNext();
            current = null;
        } else {
            current = first;
        }
        while (current != null) {
            if (current.getNext() == valve) {
                current.setNext(valve.getNext());
                break;
            }
            current = current.getNext();
        }

        if (first == basic) first = null;

        if (valve instanceof Contained)
            ((Contained) valve).setContainer(null);

        if (valve instanceof Lifecycle) {
            // Stop this valve if necessary
            if (getState().isAvailable()) {
                try {
                    ((Lifecycle) valve).stop();
                } catch (LifecycleException e) {
                    log.error(sm.getString("standardPipeline.valve.stop"), e);
                }
            }
            try {
                ((Lifecycle) valve).destroy();
            } catch (LifecycleException e) {
                log.error(sm.getString("standardPipeline.valve.destroy"), e);
            }
        }

        container.fireContainerEvent(Container.REMOVE_VALVE_EVENT, valve);
    }


    @Override
    public Valve getFirst() {
        if (first != null) {
            return first;
        }

        return basic;
    }
}