Java Reference
In-Depth Information
Once created, the JsonObject can be passed to a client for processing. In this example, the object sections are
printed to the server log, and the output looks similar to the following:
{"jsonJob":{"jobId":1,"division":"IT","title":"IT TITLE A","salary":60000}}
Persisting JSON
The JsonWriter class can be utilized to write a JsonObject to a Java writer object. A JsonWriter is instantiated by
passing a Writer object as an argument. Instantiating a JsonWriter will prepare the Writer object that had been
passed as an argument to write JSON format. After that Writer has been created, the JsonWriter writeObject()
method can be invoked, passing the JsonObject that is to be written. Once the JsonObject has been written, the
JsonWriter can be closed by calling its close() method. These are the only steps that are necessary for writing a
JSON object to a Java Writer class type.
The example below goes one step further and writes the JSON object to disk. In this case, a StringWriter
encapsulates the JsonWriter . To do so, a new FileWriter is instantiated, passing the name of the file that we wish
to create. Next, a BufferedWriter is created, passing the FileWriter that was previously instantiated. Lastly, the
contents of the StringWriter that contains the JSON object is written to the BufferedWriter by calling out.write() .
Doing so writes the content to the File that was created. When this process is complete, a new JSON object will have
been written to disk.
The following example utilizes the JSON-P API to build a JSON object, and then store it to the file system. The
JsonWriter class makes it possible to create a file on disk and then write the JSON to that file.
public void writeJson() {
try {
JsonObject jsonObject = jsonController.buildJobsJson();
StringWriter writer = new StringWriter();
JsonWriter jsonWriter = Json.createWriter(writer);
// Write file
FileWriter fstream = new FileWriter("Jobs.json");
BufferedWriter out = new BufferedWriter(fstream);
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(
FacesMessage.SEVERITY_INFO, "JSON Built",
"JSON Built"));
} catch (IOException ex) {
Parsing JSON
In order to perform some tasks, a JSON object must be searched to find only the content that is desired and useful
for the current task. Utilizing a JSON parser can make jobs such as these easier, as a parser is able to break the
object down into pieces so that each different name/value pair or attribute can be examined as needed to locate the
desired result.
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