Placeholder Resolver
Given a data source representing key => value pairs, resolve placeholders
like ${foo.bar} to the value associated with the foo.bar key in
the data source., (*1)
Placeholder Resolver is intended to be used at a relatively low level.
For example, a configuration library could use Placeholder Resolver
behind the scenes to allow for configuration values to reference
other configuration values., (*2)
Example
conn.driver: mysql
conn.db_name: example
conn.hostname: 127.0.0.1
conn.username: root
conn.password: pa$$word
Given the appropriate DataSourceInterface implementation to provide
the above data as a set of key => value pairs, the Placeholder Resolver
would resolve the value of $dsnPattern to mysql:dbname=example;host=127.0.0.1., (*3)
$dsnPattern = '${conn.driver}:dbname=${conn.db_name};host=${conn.hostname}';
$dsn = $placeholderResolver->resolveValue($dsnPattern);
// mysql:dbname=example;host=127.0.0.1
Requirements
Usage
use Dflydev\PlaceholderResolver\RegexPlaceholderResolver;
// YourDataSource implements Dflydev\PlaceholderResolver\DataSource\DataSourceInterface
$dataSource = new YourDataSource;
// Create the placeholder resolver
$placeholderResolver = new RegexPlaceholderResolver($dataSource);
// Start resolving placeholders
$value = $placeholderResolver->resolvePlaceholder('${foo}');
The RegexPlaceholderResolver constructor accepts two additional arguments,
a placeholder prefix and a placeholder suffix. The default placeholder
prefix is ${ and the default placeholder suffix is }., (*4)
To handle placeholders that look like <foo.bar> instead of ${foo.bar},
one would instantiate the class like this:, (*5)
$placeholderResolver = new RegexPlaceholderResolver($dataSource, '<', '>');
Placeholders can recursively resolve placeholders. For example, given a
data source with the following:, (*6)
array(
'foo' => 'FOO',
'bar' => 'BAR',
'FOO.BAR' => 'BAZ!',
);
The placeholder ${${foo}.${bar}} would internally be resolved to
${FOO.BAR} before being further resolved to BAZ!., (*7)
Resolved placeholders are cached using the CacheInterface. The default
Cache implementation is used unless it is explicitly set on the
Placeholder Resolver., (*8)
// YourCache implements Dflydev\PlaceholderResolver\Cache\CacheInterface
$cache = new YourCache;
$placeholderResolver->setCache($cache);
License
This library is licensed under the New BSD License - see the LICENSE file
for details., (*9)
If you have questions or want to help out, join us in the
#dflydev channel on irc.freenode.net., (*10)
Not Invented Here
Much of the ideas behind this library came from Spring's Property
Placeholder Configurer implementation., (*11)
Wallogit.com
