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package com.sun.tools.attach.spi;
import java.io.IOException;
import java.util.Collections;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.List;
import com.sun.tools.attach.VirtualMachine;
import com.sun.tools.attach.VirtualMachineDescriptor;
import com.sun.tools.attach.AttachPermission;
import com.sun.tools.attach.AttachNotSupportedException;
import java.util.ServiceLoader;
/**
* Attach provider class for attaching to a Java virtual machine.
*
* <p> An attach provider is a concrete subclass of this class that has a
* zero-argument constructor and implements the abstract methods specified
* below.
*
* <p> An attach provider implementation is typically tied to a Java virtual
* machine implementation, version, or even mode of operation. That is, a specific
* provider implementation will typically only be capable of attaching to
* a specific Java virtual machine implementation or version. For example, Sun's
* JDK implementation ships with provider implementations that can only attach to
* Sun's <i>HotSpot</i> virtual machine. In general, if an environment
* consists of Java virtual machines of different versions and from different
* vendors then there will be an attach provider implementation for each
* <i>family</i> of implementations or versions.
*
* <p> An attach provider is identified by its {@link #name <i>name</i>} and
* {@link #type <i>type</i>}. The <i>name</i> is typically, but not required to
* be, a name that corresponds to the VM vendor. The Sun JDK implementation,
* for example, ships with attach providers that use the name <i>"sun"</i>. The
* <i>type</i> typically corresponds to the attach mechanism. For example, an
* implementation that uses the Doors inter-process communication mechanism
* might use the type <i>"doors"</i>. The purpose of the name and type is to
* identify providers in environments where there are multiple providers
* installed.
*
* <p> AttachProvider implementations are loaded and instantiated at the first
* invocation of the {@link #providers() providers} method. This method
* attempts to load all provider implementations that are installed on the
* platform.
*
* <p> All of the methods in this class are safe for use by multiple
* concurrent threads.
*
* @since 1.6
*/
public abstract class AttachProvider {
private static final Object lock = new Object();
private static List<AttachProvider> providers = null;
/**
* Initializes a new instance of this class.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link com.sun.tools.attach.AttachPermission AttachPermission}
* ("{@code createAttachProvider}")
*/
protected AttachProvider() {
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(new AttachPermission("createAttachProvider"));
}
/**
* Return this provider's name.
*
* @return The name of this provider
*/
public abstract String name();
/**
* Return this provider's type.
*
* @return The type of this provider
*/
public abstract String type();
/**
* Attaches to a Java virtual machine.
*
* <p> A Java virtual machine is identified by an abstract identifier. The
* nature of this identifier is platform dependent but in many cases it will be the
* string representation of the process identifier (or pid).
*
* <p> This method parses the identifier and maps the identifier to a Java
* virtual machine (in an implementation dependent manner). If the identifier
* cannot be parsed by the provider then an
* {@link com.sun.tools.attach.AttachNotSupportedException AttachNotSupportedException}
* is thrown. Once parsed this method attempts to attach to the Java virtual machine.
* If the provider detects that the identifier corresponds to a Java virtual machine
* that does not exist, or it corresponds to a Java virtual machine that does not support
* the attach mechanism implemented by this provider, or it detects that the
* Java virtual machine is a version to which this provider cannot attach, then
* an {@code AttachNotSupportedException} is thrown.
*
* @param id
* The abstract identifier that identifies the Java virtual machine.
*
* @return VirtualMachine representing the target virtual machine.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link com.sun.tools.attach.AttachPermission AttachPermission}
* ("{@code attachVirtualMachine}"), or other permission
* required by the implementation.
*
* @throws AttachNotSupportedException
* If the identifier cannot be parsed, or it corresponds to
* to a Java virtual machine that does not exist, or it
* corresponds to a Java virtual machine which this
* provider cannot attach.
*
* @throws IOException
* If some other I/O error occurs
*
* @throws NullPointerException
* If {@code id} is {@code null}
*/
public abstract VirtualMachine attachVirtualMachine(String id)
throws AttachNotSupportedException, IOException;
/**
* Attaches to a Java virtual machine.
*
* <p> A Java virtual machine can be described using a
* {@link com.sun.tools.attach.VirtualMachineDescriptor VirtualMachineDescriptor}.
* This method invokes the descriptor's
* {@link com.sun.tools.attach.VirtualMachineDescriptor#provider() provider()} method
* to check that it is equal to this provider. It then attempts to attach to the
* Java virtual machine.
*
* @param vmd
* The virtual machine descriptor
*
* @return VirtualMachine representing the target virtual machine.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link com.sun.tools.attach.AttachPermission AttachPermission}
* ("{@code attachVirtualMachine}"), or other permission
* required by the implementation.
*
* @throws AttachNotSupportedException
* If the descriptor's
* {@link com.sun.tools.attach.VirtualMachineDescriptor#provider() provider()}
* method returns a provider that is not this provider, or it does not
* correspond to a Java virtual machine to which this provider can attach.
*
* @throws IOException
* If some other I/O error occurs
*
* @throws NullPointerException
* If {@code vmd} is {@code null}
*/
public VirtualMachine attachVirtualMachine(VirtualMachineDescriptor vmd)
throws AttachNotSupportedException, IOException
{
if (vmd.provider() != this) {
throw new AttachNotSupportedException("provider mismatch");
}
return attachVirtualMachine(vmd.id());
}
/**
* Lists the Java virtual machines known to this provider.
*
* <p> This method returns a list of
* {@link com.sun.tools.attach.VirtualMachineDescriptor} elements. Each
* {@code VirtualMachineDescriptor} describes a Java virtual machine
* to which this provider can <i>potentially</i> attach. There isn't any
* guarantee that invoking
* {@link #attachVirtualMachine(VirtualMachineDescriptor) attachVirtualMachine}
* on each descriptor in the list will succeed.
*
* @return The list of virtual machine descriptors which describe the
* Java virtual machines known to this provider (may be empty).
*/
public abstract List<VirtualMachineDescriptor> listVirtualMachines();
/**
* Returns a list of the installed attach providers.
*
* <p> An AttachProvider is installed on the platform if:
*
* <ul>
* <li>It is installed in a JAR file that is visible to the defining
* class loader of the AttachProvider type (usually, but not required
* to be, the {@link java.lang.ClassLoader#getSystemClassLoader system
* class loader}).</li>
*
* <li>The JAR file contains a provider configuration named
* {@code com.sun.tools.attach.spi.AttachProvider} in the resource directory
* {@code META-INF/services}.</li>
*
* <li>The provider configuration file lists the full-qualified class
* name of the AttachProvider implementation.</li>
* </ul>
*
* <p> The format of the provider configuration file is one fully-qualified
* class name per line. Space and tab characters surrounding each class name,
* as well as blank lines are ignored. The comment character is
* {@code '#'} ({@code 0x23}), and on each line all characters following
* the first comment character are ignored. The file must be encoded in
* UTF-8.
*
* <p> AttachProvider implementations are loaded and instantiated
* (using the zero-arg constructor) at the first invocation of this method.
* The list returned by the first invocation of this method is the list
* of providers. Subsequent invocations of this method return a list of the same
* providers. The list is unmodifiable.
*
* @return A list of the installed attach providers.
*/
public static List<AttachProvider> providers() {
synchronized (lock) {
if (providers == null) {
providers = new ArrayList<AttachProvider>();
ServiceLoader<AttachProvider> providerLoader =
ServiceLoader.load(AttachProvider.class,
AttachProvider.class.getClassLoader());
Iterator<AttachProvider> i = providerLoader.iterator();
while (i.hasNext()) {
try {
providers.add(i.next());
} catch (Throwable t) {
if (t instanceof ThreadDeath) {
ThreadDeath td = (ThreadDeath)t;
throw td;
}
// Log errors and exceptions since we cannot return them
t.printStackTrace();
}
}
}
return Collections.unmodifiableList(providers);
}
}
}