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package com.sun.tools.attach;

import com.sun.tools.attach.spi.AttachProvider;

/**
 * Describes a Java virtual machine.
 *
 * 

A VirtualMachineDescriptor is a container class used to * describe a Java virtual machine. It encapsulates an identifier that identifies * a target virtual machine, and a reference to the {@link * com.sun.tools.attach.spi.AttachProvider AttachProvider} that should be used * when attempting to attach to the virtual machine. The identifier is * implementation-dependent but is typically the process identifier (or pid) * environments where each Java virtual machine runs in its own operating system * process.

* *

A VirtualMachineDescriptor also has a {@link #displayName() displayName}. * The display name is typically a human readable string that a tool might * display to a user. For example, a tool that shows a list of Java * virtual machines running on a system might use the display name rather * than the identifier. A VirtualMachineDescriptor may be * created without a display name. In that case the identifier is * used as the display name. * *

VirtualMachineDescriptor instances are typically created by * invoking the {@link com.sun.tools.attach.VirtualMachine#list VirtualMachine.list()} * method. This returns the complete list of descriptors to describe the * Java virtual machines known to all installed {@link * com.sun.tools.attach.spi.AttachProvider attach providers}. * * @since 1.6 */ public class VirtualMachineDescriptor { private AttachProvider provider; private String id; private String displayName; private volatile int hash; // 0 => not computed /** * Creates a virtual machine descriptor from the given components. * * @param provider The AttachProvider to attach to the Java virtual machine. * @param id The virtual machine identifier. * @param displayName The display name. * * @throws NullPointerException * If any of the arguments are null */ public VirtualMachineDescriptor(AttachProvider provider, String id, String displayName) { if (provider == null) { throw new NullPointerException("provider cannot be null"); } if (id == null) { throw new NullPointerException("identifier cannot be null"); } if (displayName == null) { throw new NullPointerException("display name cannot be null"); } this.provider = provider; this.id = id; this.displayName = displayName; } /** * Creates a virtual machine descriptor from the given components. * *

This convenience constructor works as if by invoking the * three-argument constructor as follows: * *

* new {@link #VirtualMachineDescriptor(AttachProvider, String, String) * VirtualMachineDescriptor}(provider,  id,  id); *
* *

That is, it creates a virtual machine descriptor such that * the display name is the same as the virtual machine * identifier. * * @param provider The AttachProvider to attach to the Java virtual machine. * @param id The virtual machine identifier. * * @throws NullPointerException * If provider or id is null. */ public VirtualMachineDescriptor(AttachProvider provider, String id) { this(provider, id, id); } /** * Return the AttachProvider that this descriptor references. * * @return The AttachProvider that this descriptor references. */ public AttachProvider provider() { return provider; } /** * Return the identifier component of this descriptor. * * @return The identifier component of this descriptor. */ public String id() { return id; } /** * Return the display name component of this descriptor. * * @return The display name component of this descriptor. */ public String displayName() { return displayName; } /** * Returns a hash-code value for this VirtualMachineDescriptor. The hash * code is based upon the descriptor's components, and satifies * the general contract of the {@link java.lang.Object#hashCode() * Object.hashCode} method. * * @return A hash-code value for this descriptor. */ public int hashCode() { if (hash != 0) { return hash; } hash = provider.hashCode() * 127 + id.hashCode(); return hash; } /** * Tests this VirtualMachineDescriptor for equality with another object. * *

If the given object is not a VirtualMachineDescriptor then this * method returns false. For two VirtualMachineDescriptors to * be considered equal requires that they both reference the same * provider, and their {@link #id() identifiers} are equal.

* *

This method satisfies the general contract of the {@link * java.lang.Object#equals(Object) Object.equals} method.

* * @param ob The object to which this object is to be compared * * @return true if, and only if, the given object is * a VirtualMachineDescriptor that is equal to this * VirtualMachineDescriptor. */ public boolean equals(Object ob) { if (ob == this) return true; if (!(ob instanceof VirtualMachineDescriptor)) return false; VirtualMachineDescriptor other = (VirtualMachineDescriptor)ob; if (other.provider() != this.provider()) { return false; } if (!other.id().equals(this.id())) { return false; } return true; } /** * Returns the string representation of the VirtualMachineDescriptor. */ public String toString() { String s = provider.toString() + ": " + id; if (displayName != id) { s += " " + displayName; } return s; } }




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