1docs::api::ModPerl::MetUhsoedrLoCooknutpr(i3b)uted PerldDooccsu:m:eanptia:t:iMoondPerl::MethodLookup(3)
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6 ModPerl::MethodLookup -- Lookup mod_perl modules, objects and methods
7
9 use ModPerl::MethodLookup;
10 # return all module names containing XS method 'print'
12 my ($hint, @modules) =
13 ModPerl::MethodLookup::lookup_method('print');
14 # return only module names containing method 'print' which
16 # expects the first argument to be of type 'Apache2::Filter'
17 # (here $filter is an Apache2::Filter object)
18 my ($hint, @modules) =
19 ModPerl::MethodLookup::lookup_method('print', $filter);
20 # or
21 my ($hint, @modules) =
22 ModPerl::MethodLookup::lookup_method('print', 'Apache2::Filter');
23 # what XS methods defined by module 'Apache2::Filter'
25 my ($hint, @methods) =
26 ModPerl::MethodLookup::lookup_module('Apache2::Filter');
27 # what XS methods can be invoked on the object $r (or a ref)
29 my ($hint, @methods) =
30 ModPerl::MethodLookup::lookup_object($r);
31 # or
32 my ($hint, @methods) =
33 ModPerl::MethodLookup::lookup_object('Apache2::RequestRec');
34 # preload all mp2 modules in startup.pl
36 ModPerl::MethodLookup::preload_all_modules();
37 # command line shortcuts
39 % perl -MModPerl::MethodLookup -e print_module \
40 Apache2::RequestRec Apache2::Filter
41 % perl -MModPerl::MethodLookup -e print_object Apache2
42 % perl -MModPerl::MethodLookup -e print_method \
43 get_server_built request
44 % perl -MModPerl::MethodLookup -e print_method read
45 % perl -MModPerl::MethodLookup -e print_method read APR::Bucket
46
48 mod_perl 2.0 provides many methods, which reside in various modules.
49 One has to load each of the modules before using the desired methods.
50 "ModPerl::MethodLookup" provides the Perl API for finding module names
51 which contain methods in question and other helper functions, to find
52 out out what methods defined by some module, what methods can be called
53 on a given object, etc.
54
56 "lookup_method()"
57 Find modules (packages) containing a certain method
58 ($hint, @modules) = lookup_method($method_name);
60 ($hint, @modules) = lookup_method($method_name, $object);
61 ($hint, @modules) = lookup_method($method_name, $class));
62 arg1: $method_name ( string )
64 the method name to look up
65 opt arg2: $object or $class
67 a blessed object or the name of the class it's blessed into. If
68 there is more than one match, this extra information is used to
69 return only modules containing methods operating on the objects of
70 the same kind.
71 If a sub-classed object is passed it'll be handled correctly, by
73 checking its super-class(es). This usage is useful when the
74 "AUTOLOAD" is used to find a not yet loaded module which include
75 the called method.
76 ret1: $hint
78 a string containing a human readable lookup result, suggesting
79 which modules should be loaded, ready for copy-n-paste or
80 explaining the failure if the lookup didn't succeed.
81 ret2: @modules
83 an array of modules which have matched the query, i.e. the names of
84 the modules which contain the requested method.
85 since: 2.0.00
87 Examples:
89 Return all module names containing XS method print:
91 my ($hint, @modules) =
93 ModPerl::MethodLookup::lookup_method('print');
94 Return only module names containing method print which expects the
96 first argument to be of type "Apache2::Filter":
97 my $filter = bless {}, 'Apache2::Filter';
99 my ($hint, @modules) =
100 ModPerl::MethodLookup::lookup_method('print', $filter);
101 or:
103 my ($hint, @modules) =
105 ModPerl::MethodLookup::lookup_method('print', 'Apache2::Filter');
106 "lookup_module()"
108 Find methods contained in a certain module (package)
109 ($hint, @methods) = lookup_module($module_name);
111 arg1: $module_name ( string )
113 the module name
114 ret1: $hint
116 a string containing a human readable lookup result, suggesting,
117 which methods the module $module_name implements, or explaining the
118 failure if the lookup failed.
119 ret2: @methods
121 an array of methods which have matched the query, i.e. the names of
122 the methods defined in the requested module.
123 since: 2.0.00
125 Example:
127 What XS methods defined by module "Apache2::Filter":
129 my ($hint, @methods) =
131 ModPerl::MethodLookup::lookup_module('Apache2::Filter');
132 "lookup_object()"
134 ($hint, @methods) = lookup_object($object);
135 ($hint, @methods) = lookup_object($class);
136 arg1: $object or $class
138 an object or a name of a class an object is blessed into
139 If a sub-classed object is passed it'll be handled correctly, by
141 including methods provided by its super-class(es).
142 ret1: $hint
144 a string containing a human readable lookup result, suggesting,
145 which methods the given object can invoke (including module names
146 that need to be loaded to use those methods), or explaining the
147 failure if the lookup failed.
148 ret2: @methods
150 an array of methods which have matched the query, i.e. the names of
151 the methods that can be invoked on the given object (or its class
152 name).
153 since: 2.0.00
155 META: As of this writing this function may miss some of the
157 functions/methods that can be invoked on the given object. Currently we
158 can't programmatically deduct the objects they are invoked on, because
159 these methods are written in pure XS and manipulate the arguments stack
160 themselves. Currently these are mainly XS functions, not methods, which
161 of course aren't invoked on objects. There are also logging function
162 wrappers ("Apache2::Log").
163 Examples:
165 What XS methods can be invoked on the object $r:
167 my ($hint, @methods) =
169 ModPerl::MethodLookup::lookup_object($r);
170 or $r's class -- "Apache2::RequestRec":
172 my ($hint, @methods) =
174 ModPerl::MethodLookup::lookup_object('Apache2::RequestRec');
175 "preload_all_modules()"
177 The function "preload_all_modules()" preloads all mod_perl 2.0 modules,
178 which implement their API in XS. This is similar to the mod_perl 1.0
179 behavior which has most of its methods loaded at the startup.
180 CPAN modules developers should make sure their distribution loads each
182 of the used mod_perl 2.0 modules explicitly, and not use this function,
183 as it takes the fine control away from the users. One should avoid
184 doing this the production server (unless all modules are used indeed)
185 in order to save memory.
186 since: 2.0.00
188 "print_method()"
190 "print_method()" is a convenience wrapper for "lookup_method()", mainly
191 designed to be used from the command line. For example to print all the
192 modules which define method read execute:
193 % perl -MModPerl::MethodLookup -e print_method read
195 Since this will return more than one module, we can narrow the query to
197 only those methods which expect the first argument to be blessed into
198 class "APR::Bucket":
199 % perl -MModPerl::MethodLookup -e print_method read APR::Bucket
201 You can pass more than one method and it'll perform a lookup on each of
203 the methods. For example to lookup methods "get_server_built" and
204 "request" you can do:
205 % perl -MModPerl::MethodLookup -e print_method \
207 get_server_built request
208 The function "print_method()" is exported by default.
210 since: 2.0.00
212 "print_module()"
214 "print_module()" is a convenience wrapper for "lookup_module()", mainly
215 designed to be used from the command line. For example to print all the
216 methods defined in the module "Apache2::RequestRec", followed by
217 methods defined in the module "Apache2::Filter" you can run:
218 % perl -MModPerl::MethodLookup -e print_module \
220 Apache2::RequestRec Apache2::Filter
221 The function "print_module()" is exported by default.
223 since: 2.0.00
225 "print_object()"
227 "print_object()" is a convenience wrapper for "lookup_object()", mainly
228 designed to be used from the command line. For example to print all the
229 methods that can be invoked on object blessed into a class
230 "Apache2::RequestRec" run:
231 % perl -MModPerl::MethodLookup -e print_object \
233 Apache2::RequestRec
234 Similar to "print_object()", more than one class can be passed to this
236 function.
237 The function "print_object()" is exported by default.
239 since: 2.0.00
241
243 "AUTOLOAD"
244 When Perl fails to locate a method it checks whether the package the
245 object belongs to has an "AUTOLOAD" function defined and if so, calls
246 it with the same arguments as the missing method while setting a global
247 variable $AUTOLOAD (in that package) to the name of the originally
248 called method. We can use this facility to lookup the modules to be
249 loaded when such a failure occurs. Though since we have many packages
250 to take care of we will use a special "UNIVERSAL::AUTOLOAD" function
251 which Perl calls if can't find the "AUTOLOAD" function in the given
252 package.
253 In that function you can query "ModPerl::MethodLookup", require() the
255 module that includes the called method and call that method again using
256 the goto() trick:
257 use ModPerl::MethodLookup;
259 sub UNIVERSAL::AUTOLOAD {
260 my ($hint, @modules) =
261 ModPerl::MethodLookup::lookup_method($UNIVERSAL::AUTOLOAD, @_);
262 if (@modules) {
263 eval "require $_" for @modules;
264 goto &$UNIVERSAL::AUTOLOAD;
265 }
266 else {
267 die $hint;
268 }
269 }
270 However we don't endorse this approach. It's a better approach to
272 always abort the execution which printing the $hintand use fix the code
273 to load the missing module. Moreover installing "UNIVERSAL::AUTOLOAD"
274 may cause a lot of problems, since once it's installed Perl will call
275 it every time some method is missing (e.g. undefined "DESTROY"
276 methods). The following approach seems to somewhat work for me. It
277 installs "UNIVERSAL::AUTOLOAD" only when the the child process starts.
278 httpd.conf:
280 -----------
281 PerlChildInitHandler ModPerl::MethodLookupAuto
282 startup.pl:
284 -----------
285 {
286 package ModPerl::MethodLookupAuto;
287 use ModPerl::MethodLookup;
288 use Carp;
290 sub handler {
291 *UNIVERSAL::AUTOLOAD = sub {
293 my $method = $AUTOLOAD;
294 return if $method =~ /DESTROY/; # exclude DESTROY resolving
295 my ($hint, @modules) =
297 ModPerl::MethodLookup::lookup_method($method, @_);
298 $hint ||= "Can't find method $AUTOLOAD";
299 croak $hint;
300 };
301 return 0;
302 }
303 }
304 This example doesn't load the modules for you. It'll print to STDERR
306 what module should be loaded, when a method from the not-yet-loaded
307 module is called.
308 A similar technique is used by "Apache2::porting".
310 META: there is a better version of AUTOLOAD discussed on the dev list.
312 Replace the current one with it. (search the archive for EazyLife)
313 Command Line Lookups
315 When a method is used and mod_perl has reported a failure to find it,
316 it's often useful to use the command line query to figure out which
317 module needs to be loaded. For example if when executing:
318 $r->construct_url();
320 mod_perl complains:
322 Can't locate object method "construct_url" via package
324 "Apache2::RequestRec" at ...
325 you can ask "ModPerl::MethodLookup" for help:
327 % perl -MModPerl::MethodLookup -e print_method construct_url
329 To use method 'construct_url' add:
330 use Apache2::URI ();
331 and after copy-n-pasting the use statement in our code, the problem
333 goes away.
334 One can create a handy alias for this technique. For example, C-style
336 shell users can do:
337 % alias lookup "perl -MModPerl::MethodLookup -e print_method"
339 For Bash-style shell users:
341 % alias lookup="perl -MModPerl::MethodLookup -e print_method"
343 Now the lookup is even easier:
345 % lookup construct_url
347 to use method 'construct_url' add:
348 use Apache2::URI;
349 Similar aliases can be provided for "print_object()" and
351 "print_module()".
352
354 These methods aren't yet picked by this module (the extract from the
355 map file):
356 modperl_filter_attributes | MODIFY_CODE_ATTRIBUTES
358 modperl_spawn_proc_prog | spawn_proc_prog
359 apr_ipsubnet_create | new
360 Please report to the mod_perl development mailing list if you find any
362 other missing methods. But remember that as of this moment the module
363 reports only XS functions. In the future we may add support for pure
364 perl functions/methods as well.
365
367 · the mod_perl 1.0 backward compatibility document
368 · porting Perl modules
370 · porting XS modules
372 · "Apache2::porting"
374
376 mod_perl 2.0 and its core modules are copyrighted under The Apache
377 Software License, Version 2.0.
378
380 The mod_perl development team and numerous contributors.
381perl v5.32.0 2020-07-28docs::api::ModPerl::MethodLookup(3)