6875716: JLayer.remove((Component)null) should behave consistently in (not) throwing NPE
Reviewed-by: rupashka
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Command line HSDB
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<h1>Command line HSDB</h1>
<p>
When debugging remote core dumps it is easier to work with command line tools instead of
GUI tools. Command line HSDB (CLHSDB) tool is alternative to SA GUI tool HSDB.
</p>
<p>
There is also JavaScript based SA command line interface called <a href="jsdb.html">jsdb</a>.
But, CLHSDB supports Unix shell-like (or dbx/gdb-like) command line interface with
support for output redirection/appending (familiar >, >>), command history and so on.
Each CLHSDB command can have zero or more arguments and optionally end with output redirection
(or append) to a file. Commands may be stored in a file and run using <b>source</b> command.
<b>help</b> command prints usage message for all supported commands (or a specific command)
</p>
<h3>Shell/batch scripts to run command line HSDB</h3>
<ul>
<li>clhsdbproc.sh
<li>clhsdbproc64.sh
<li>clhsdbwindbg.bat
<li>clhsdbwindbg64.bat
</ul>
<h3>Annotated output of CLHSDB help command</h3>
<pre>
<code>
Available commands:
assert true | false <font color="red">turn on/off asserts in SA code</font>
attach pid | exec core <font color="red">attach SA to a process or core</font>
class name <font color="red">find a Java class from debuggee and print oop</font>
classes <font color="red">print all loaded Java classes with klassOop</font>
detach <font color="red">detach SA from current target</font>
dis address [ length ] <font color="red">disassemble (sparc/x86) specified number of instructions from given address</font>
dumpclass { address | name } [ directory ] <font color="red">dump .class file for given klassOop or class name</font>
dumpheap [ file ] <font color="red">dump heap in hprof binary format</font>
echo [ true | false ] <font color="red">turn on/off command echo mode</font>
examine [ address/count ] | [ address,address] <font color="red">show contents of memory from given address</font>
field [ type [ name fieldtype isStatic offset address ] ] <font color="red">print info about a field of HotSpot type</font>
findpc address <font color="red">print info. about pointer location</font>
flags [ flag ] <font color="red">show all -XX flag name value pairs. or just show given flag</font>
help [ command ] <font color="red">print help message for all commands or just given command</font>
history <font color="red">show command history. usual !command-number syntax works.</font>
inspect expression <font color="red">inspect a given oop</font>
jdis address <font color="red">show bytecode disassembly of a given methodOop</font>
jhisto <font color="red">show Java heap histogram</font>
jseval script <font color="red">evaluate a given string as JavaScript code</font>
jsload file <font color="red">load and evaluate a JavaScript file</font>
jstack [-v] <font color="red">show Java stack trace of all Java threads. -v is verbose mode</font>
livenmethods <font color="red">show all live nmethods</font>
mem address [ length ] <font color="red">show contents of memory -- also shows closest ELF/COFF symbol if found</font>
pmap <font color="red">show Solaris pmap-like output</font>
print expression <font color="red">print given klassOop, methodOop or arbitrary address</font>
printas type expression <font color="red">print given address as given HotSpot type. eg. print JavaThread <address></font>
printstatics [ type ] <font color="red">print static fields of given HotSpot type (or all types if none specified)</font>
pstack [-v] <font color="red">show mixed mode stack trace for all Java, non-Java threads. -v is verbose mode</font>
quit <font color="red">quit CLHSDB tool</font>
reattach <font color="red">detach and re-attach SA to current target</font>
scanoops start end [ type ] <font color="red">scan a Oop from given start to end address</font>
search [ heap | codecache | threads ] value <font color="red">search a value in heap or codecache or threads</font>
source filename <font color="red">load and execute CLHSDB commands from given file</font>
symbol name <font color="red">show address of a given ELF/COFF symbol</font>
sysprops <font color="red">show all Java System properties</font>
threads <font color="red">show all Java threads</font>
tokenize ...
type [ type [ name super isOop isInteger isUnsigned size ] ] <font color="red">show info. on HotSpot type</font>
universe <font color="red">print gc universe</font>
verbose true | false <font color="red">turn on/off verbose mode</font>
versioncheck [ true | false ] <font color="red">turn on/off debuggee VM version check</font>
whatis address <font color="red">print info about any arbitrary address</font>
where { -a | id } <font color="red">print Java stack trace of given Java thread or all Java threads (-a)</font>
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<h3>JavaScript integration</h3>
<p>Few CLHSDB commands are already implemented in JavaScript. It is possible to extend CLHSDB command set
by implementing more commands in a JavaScript file and by loading it by <b>jsload</b> command. <b>jseval</b>
command may be used to evaluate arbitrary JavaScript expression from a string. Any JavaScript function
may be exposed as a CLHSDB command by registering it using JavaScript <b><code>registerCommand</code></b>
function. This function accepts command name, usage and name of the JavaScript implementation function
as arguments.
</p>
<h3>Simple CLHSDB command implemented in JavaScript</h3>
<b>File: test.js</b>
<pre>
<code>
function helloImpl(name) {
println("hello, " + name);
}
// register the above JavaScript function as CLHSDB command
registerCommand("hello", "hello name", "helloImpl");
</code>
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"test.js" can be loaded in CLHSDB prompt using <b>jsload</b> command using
<pre>
<code>
hsdb> jsload test.js
</code>
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