gson使用教程-翻譯3

原文地址:http://www.studytrails.com/java/json/java-google-json-parse-json-to-java-tree.jsp

在之前的教程中，我們看到怎樣將一段json字符串轉換成Java對象.在這節中,我們將把json轉換成樹結構的JsonElement.遍歷這個樹對象可以生成對應的java對象.JsonElement這個類有isJsonObject(),isJsonNull()等這些用來判斷JsonElement的方法.有getAsJsonObject(),getAsJsonPrimitive()等獲取實際對象的方法.接下來，我們將解析從free music

archiver返回的json,代碼如下:

package com.studytrails.json.gson;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import org.apache.commons.io.IOUtils;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
public class ParseTreeExample6 {
    public static void main(String[] args) throws MalformedURLException, IOException {
        String url = "http://freemusicarchive.org/api/get/albums.json?api_key=60BLHNQCAOUFPIBZ&limit=5";
        String json = IOUtils.toString(new URL(url));
        JsonParser parser = new JsonParser();
        // The JsonElement is the root node. It can be an object, array, null or
        // java primitive.
        JsonElement element = parser.parse(json);
        // use the isxxx methods to find out the type of jsonelement. In our
        // example we know that the root object is the Albums object and
        // contains an array of dataset objects
        if (element.isJsonObject()) {
            JsonObject albums = element.getAsJsonObject();
            System.out.println(albums.get("title").getAsString());
            JsonArray datasets = albums.getAsJsonArray("dataset");
            for (int i = 0; i < datasets.size(); i++) {
                JsonObject dataset = datasets.get(i).getAsJsonObject();
                System.out.println(dataset.get("album_title").getAsString());
            }
        }

    }
}