JsonGetArray

从JSON字符串中寻找一个特定key的数组

public class JsonGetArray {

public static int nextIndexOf(String str, int fromIndex, char ch) throws Exception {
	int ret = -1;
	if (ch == ' ' || ch == '\r' || ch == '\n' || ch == '\t') {
		ret = str.indexOf(ch, fromIndex);
	} else {
		char thisChar;
		int i = fromIndex;
		while (i < str.length()) {
			thisChar = str.charAt(i);
			switch(thisChar) {
			case ' ':
			case '\t':
			case '\r':
			case '\n':
				i++;
				continue;
			default:
				if (thisChar == ch) {
					ret = i;
				} else {
					throw new Exception("unexpected char : " + thisChar);
				}
				break;
			}
			if (ret > -1) break;
		}
	}
	return ret;
}

public static String[] getArray(String json, String key) throws Exception {
	String[] ret = null;
	if (json != null && key != null && !"".equals(json) && !"".equals(key)) {
		int keyLength = key.length();
		int startIndex = json.indexOf("\"" + key + "\"");
		if (startIndex > -1) {
			int colonIndex = nextIndexOf(json, startIndex + keyLength + 2, ':');
			int arrStart = nextIndexOf(json, colonIndex + 1, '[');
			int arrEnd = json.indexOf(']', arrStart + 1);
			if (arrEnd > -1) {
				String subStr = json.substring(arrStart + 1, arrEnd);
				String[] list = subStr.split(",");
				if (list.length > 0) {
					ret = new String[list.length];
					int leftquot, rightquot;
					for (int i = 0; i < list.length; i++) {
						leftquot = list[i].indexOf('"');
						if (leftquot > -1) {
							rightquot = list[i].indexOf('"', leftquot + 1);
							if (rightquot > -1) {
								ret[i] = list[i].substring(leftquot + 1, rightquot);
								continue;
							}
						}
						throw new Exception("Incomplete quotation marks");
					}
				}
			}
		}
	}
	return ret;
}

public static void main(String[] args) {
	String str = "{\"name\":\"张三\", \"age\":\"14\",\"friends\":[\"小明\", \"小红\"]}";
	String key = "friends";
	try {
		String[] arr = getArray(str, key);
		for (int i = 0; i < arr.length; i++) {
			System.out.println(arr[i]);
		}
	} catch (Exception e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
}

}