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Diffstat (limited to 'doc/jsoncpp.dox')
| -rw-r--r-- | doc/jsoncpp.dox | 137 |
1 files changed, 91 insertions, 46 deletions
diff --git a/doc/jsoncpp.dox b/doc/jsoncpp.dox index a9ed47e..f340591 100644 --- a/doc/jsoncpp.dox +++ b/doc/jsoncpp.dox @@ -3,36 +3,46 @@ \section _intro Introduction <a HREF="http://www.json.org/">JSON (JavaScript Object Notation)</a> - is a lightweight data-interchange format. -It can represent integer, real number, string, an ordered sequence of value, and -a collection of name/value pairs. + is a lightweight data-interchange format. Here is an example of JSON data: \verbatim +{ + "encoding" : "UTF-8", + "plug-ins" : [ + "python", + "c++", + "ruby" + ], + "indent" : { "length" : 3, "use_space": true } +} +\endverbatim +<b>JsonCpp</b> supports comments as <i>meta-data</i>: +\code // Configuration options { // Default encoding for text "encoding" : "UTF-8", - + // Plug-ins loaded at start-up "plug-ins" : [ "python", - "c++", + "c++", // trailing comment "ruby" ], - + // Tab indent size - "indent" : { "length" : 3, "use_space": true } + // (multi-line comment) + "indent" : { /*embedded comment*/ "length" : 3, "use_space": true } } -\endverbatim -<code>jsoncpp</code> supports comments as <i>meta-data</i>. +\endcode \section _features Features - read and write JSON document - attach C++ style comments to element during parsing - rewrite JSON document preserving original comments -Notes: Comments used to be supported in JSON but where removed for +Notes: Comments used to be supported in JSON but were removed for portability (C like comments are not supported in Python). Since comments are useful in configuration/input file, this feature was preserved. @@ -40,51 +50,81 @@ preserved. \section _example Code example \code -Json::Value root; // will contains the root value after parsing. -Json::Reader reader; -bool parsingSuccessful = reader.parse( config_doc, root ); -if ( !parsingSuccessful ) -{ - // report to the user the failure and their locations in the document. - std::cout << "Failed to parse configuration\n" - << reader.getFormattedErrorMessages(); - return; -} +Json::Value root; // 'root' will contain the root value after parsing. +std::cin >> root; -// Get the value of the member of root named 'encoding', return 'UTF-8' if there is no -// such member. +// You can also read into a particular sub-value. +std::cin >> root["subtree"]; + +// Get the value of the member of root named 'encoding', +// and return 'UTF-8' if there is no such member. std::string encoding = root.get("encoding", "UTF-8" ).asString(); -// Get the value of the member of root named 'encoding', return a 'null' value if + +// Get the value of the member of root named 'plug-ins'; return a 'null' value if // there is no such member. const Json::Value plugins = root["plug-ins"]; -for ( int index = 0; index < plugins.size(); ++index ) // Iterates over the sequence elements. + +// Iterate over the sequence elements. +for ( int index = 0; index < plugins.size(); ++index ) loadPlugIn( plugins[index].asString() ); - -setIndentLength( root["indent"].get("length", 3).asInt() ); -setIndentUseSpace( root["indent"].get("use_space", true).asBool() ); -// ... -// At application shutdown to make the new configuration document: -// Since Json::Value has implicit constructor for all value types, it is not -// necessary to explicitly construct the Json::Value object: -root["encoding"] = getCurrentEncoding(); -root["indent"]["length"] = getCurrentIndentLength(); -root["indent"]["use_space"] = getCurrentIndentUseSpace(); - -Json::StyledWriter writer; -// Make a new JSON document for the configuration. Preserve original comments. -std::string outputConfig = writer.write( root ); - -// You can also use streams. This will put the contents of any JSON -// stream at a particular sub-value, if you'd like. -std::cin >> root["subtree"]; +// Try other datatypes. Some are auto-convertible to others. +foo::setIndentLength( root["indent"].get("length", 3).asInt() ); +foo::setIndentUseSpace( root["indent"].get("use_space", true).asBool() ); + +// Since Json::Value has an implicit constructor for all value types, it is not +// necessary to explicitly construct the Json::Value object. +root["encoding"] = foo::getCurrentEncoding(); +root["indent"]["length"] = foo::getCurrentIndentLength(); +root["indent"]["use_space"] = foo::getCurrentIndentUseSpace(); -// And you can write to a stream, using the StyledWriter automatically. +// If you like the defaults, you can insert directly into a stream. std::cout << root; +// Of course, you can write to `std::ostringstream` if you prefer. + +// If desired, remember to add a linefeed and flush. +std::cout << std::endl; +\endcode + +\section _advanced Advanced usage + +Configure *builders* to create *readers* and *writers*. For +configuration, we use our own `Json::Value` (rather than +standard setters/getters) so that we can add +features without losing binary-compatibility. + +\code +// For convenience, use `writeString()` with a specialized builder. +Json::StreamWriterBuilder wbuilder; +wbuilder["indentation"] = "\t"; +std::string document = Json::writeString(wbuilder, root); + +// Here, using a specialized Builder, we discard comments and +// record errors as we parse. +Json::CharReaderBuilder rbuilder; +rbuilder["collectComments"] = false; +std::string errs; +bool ok = Json::parseFromStream(rbuilder, std::cin, &root, &errs); +\endcode + +Yes, compile-time configuration-checking would be helpful, +but `Json::Value` lets you +write and read the builder configuration, which is better! In other words, +you can configure your JSON parser using JSON. + +CharReaders and StreamWriters are not thread-safe, but they are re-usable. +\code +Json::CharReaderBuilder rbuilder; +cfg >> rbuilder.settings_; +std::unique_ptr<Json::CharReader> const reader(rbuilder.newCharReader()); +reader->parse(start, stop, &value1, &errs); +// ... +reader->parse(start, stop, &value2, &errs); +// etc. \endcode \section _pbuild Build instructions -The build instructions are located in the file +The build instructions are located in the file <a HREF="https://github.com/open-source-parsers/jsoncpp/blob/master/README.md">README.md</a> in the top-directory of the project. The latest version of the source is available in the project's GitHub repository: @@ -92,7 +132,7 @@ The latest version of the source is available in the project's GitHub repository jsoncpp</a> \section _news What's New? -The description of latest changes can be found in +The description of latest changes can be found in <a HREF="https://github.com/open-source-parsers/jsoncpp/wiki/NEWS"> the NEWS wiki </a>. @@ -112,8 +152,13 @@ The description of latest changes can be found in \section _license License See file <a href="https://github.com/open-source-parsers/jsoncpp/blob/master/LICENSE"><code>LICENSE</code></a> in the top-directory of the project. -Basically JsonCpp is licensed under MIT license, or public domain if desired +Basically JsonCpp is licensed under MIT license, or public domain if desired and recognized in your jurisdiction. \author Baptiste Lepilleur <blep@users.sourceforge.net> (originator) +\author Christopher Dunn <cdunn2001@gmail.com> (primary maintainer) +\version \include version +We make strong guarantees about binary-compatibility, consistent with +<a href="http://apr.apache.org/versioning.html">the Apache versioning scheme</a>. +\sa version.h */ |