Overview (Java Debug Interface )
Keywords: Overview, Java&trade; Debug Interface
Date: 2018-03-02

# Java™ Debug Interface

The JavaTM Debug Interface (JDI) is a high level Java API providing information useful for debuggers and similar systems needing access to the running state of a (usually remote) virtual machine.

See: Description

Packages
Package | Description
--- | ---
com.sun.jdi | This is the core package of the Java Debug Interface (JDI), it defines mirrors for values, types, and the target VirtualMachine itself - as well bootstrapping facilities.
com.sun.jdi.connect | This package defines connections between the virtual machine using the JDI and the target virtual machine.
com.sun.jdi.connect.spi | This package comprises the interfaces and classes used to develop new `TransportService` implementations.
com.sun.jdi.event | This package defines JDI events and event processing.
com.sun.jdi.request | This package is used to request that a JDI event be sent under specified conditions.

The JavaTM Debug Interface (JDI) is a high level Java API providing information useful for debuggers and similar systems needing access to the running state of a (usually remote) virtual machine.

The JDI provides introspective access to a running virtual machine's state, Class, Array, Interface, and primitive types, and instances of those types.

The JDI also provides explicit control over a virtual machine's execution. The ability to suspend and resume threads, and to set breakpoints, watchpoints, ... Notification of exceptions, class loading, thread creation... The ability to inspect a suspended thread's state, local variables, stack backtrace...

JDI is the highest-layer of the Java Platform Debugger Architecture (JPDA). For more information on the Java Platform Debugger Architecture, see the Java Platform Debugger Architecture documentation for this release and the Java Platform Debugger Architecture website.

Global Exceptions:

This section documents exceptions which apply to the entire API and are thus not documented on individual methods.

> `VMMismatchException`

> Any method on a `Mirror` that takes a `Mirror` as an parameter directly or indirectly (e.g., as a element in a `List`) will throw `VMMismatchException` if the mirrors are from different virtual machines.

> `NullPointerException`

> Any method which takes a `Object` as an parameter will throw `NullPointerException` if null is passed directly or indirectly -- unless null is explicitly mentioned as a valid parameter.

NOTE: The exceptions below may be thrown whenever the specified conditions are met but a guarantee that they are thrown only exists when a valid result cannot be returned.

> `VMDisconnectedException`

> Any method on `ObjectReference`, `ReferenceType`, `EventRequest`, `StackFrame`, or `VirtualMachine` or which takes one of these directly or indirectly as an parameter may throw `VMDisconnectedException` if the target VM is disconnected and the `VMDisconnectEvent` has been or is available to be read from the `EventQueue`.

> `VMOutOfMemoryException`

> Any method on `ObjectReference`, `ReferenceType`, `EventRequest`, `StackFrame`, or `VirtualMachine` or which takes one of these directly or indirectly as an parameter may throw `VMOutOfMemoryException` if the target VM has run out of memory.

> `ObjectCollectedException`

> Any method on `ObjectReference` or which directly or indirectly takes `ObjectReference` as parameter may throw `ObjectCollectedException` if the mirrored object has been garbage collected.

> Any method on `ReferenceType` or which directly or indirectly takes `ReferenceType` as parameter may throw `ObjectCollectedException` if the mirrored type has been unloaded.

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