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Plug-in
Programmer's Guide Netscape Directory Server |
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This chapter describes how to write entry store and entry fetch plug-ins. You can use these types of plug-ins to invoke functions before and after data is read from the default database.
The chapter contains the following sections:
Entry store plug-in functions are called before data is written to the database. Entry fetch plug-in functions are called after data is read from the default database. This processing is illustrated in Figure 9-1.
Unlike most other types of plug-in functions, entry store and entry fetch plug-in functions are not passed a parameter block when called. Instead, entry store and entry fetch plug-in functions must have the following prototype:
void function_name( char **entry, unsigned long *len );
On Windows platforms, use the following prototype, and make sure to include the function in a .def file:
__declspec(
dllexport ) \
void
function_name( char **entry, unsigned long *len );
The parameters are described below:
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entry |
Pointer to a string specifying the entry in LDIF format; for details on this format, see slapi_filter_free(). |
Since the text of the entry is passed in as
an argument, you can modify the entry before it gets saved to disk and
modify the entry after it is read from disk.
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For example entry store and entry fetch plug-in functions, check this source file in your installation: <server_root>/plugins/slapd/slapi/examples/testentry.c
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Unlike most other types of plug-in functions, you do not register an entry store or entry fetch plug-in function by setting the function name in the parameter block. Instead, you specify the function name directly in the server configuration file.
For current versions of Directory Server, shut down the server, add the plug-in parameters to the dse.ldif file, and restart the server (see chapter 3, "Configuring Plug-ins"). For example, your plug-in entry might look like this:
dn: cn=Test
entry,cn=plugins,cn=config
objectClass:
top
objectClass:
nsSlapdPlugin
objectClass:
extensibleObject
cn: Test entry
nsslapd-pluginPath:
/usr/netscape/servers/plugins/slapd/slapi/
examples/libtest-plugin.so
nsslapd-pluginInitfunc:
testentry_init
nsslapd-pluginType:
ldbmentryfetchstore
nsslapd-pluginEnabled:
on
nsslapd-pluginId:
test-entry
For an example plug-in function that implements entry store and entry fetch operations, take a look at this source file:
<server_root>/plugins/slapd/slapi/examples/testentry.c
In Directory Server 4.x, add a directive to the slapd.ldbm.conf file in the following form to specify the name and location of your plug-in function:
plugin entrystore
[on|off] "<name of plugin>" \
<library_name> <function_name>
plugin entryfetch
[on|off] "<name of plugin>" \
<library_name> <function_name>
<library_name> is the name and path to your shared library or dynamic link library, and <function_name> is the name of your plug-in function.
For example, the following directives register the function named my_store() as the entry store plug-in function and my_fetch() as the entry fetch plug-in function. Both functions are defined in the library /usr/nslib/myentry.so.
plugin entrystore
on
"my
entrystore plugin" \
/serverroot/myentry.so my_store
plugin entryfetch on
"my entryfetch plugin" \
/serverroot/myentry.so my_fetch
Each entry store and entry fetch plug-in is
associated with the default ldbm backend. Make sure that the plugin
directive that registers the plug-in is within the database section for
ldbm in the slapd.ldbm.conf
file for Directory Server 4.x. The plugin
directive should be after the
database ldbm
directive and before the next database
directive, if there are any.
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