如何将我的java对象转换为json并将其保存在SD卡中

Question

我不知道如何在此之后将我的Java转换为JSON与Jackson

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ObjectMapper mapper = new ObjectMapper();

    Book b = new Book();
    ArrayList<Book> listBook = new ArrayList<Book>();
    listBook.add(b);

    b = new Book();
    b.setName("exam");
    b.setFileName("res/raw/exam.txt");
    b.setCate(0); //4 categories here
    b.setSoundFileName("res/raw/exams.mp3");
    b.setTranFileName("res/raw/examt.txt");
    listBook.add(b);

    b = new Book();
    b.setName("test");
    b.setCate(0);
    b.setFileName("res/raw/test.txt");
    b.setSoundFileName("res/raw/tests.mp3")
    b.setTranFileName("res/raw/textt.txt");

    String jsonString = "";
    try {
        jsonString = mapper.writeValueAsString(listBook);
    } catch (JsonGenerationException e) {

        e.printStackTrace();
    } catch (JsonMappingException e) {

        e.printStackTrace();
    } catch (IOException e) {

        e.printStackTrace();
    }

    Log.d("ttt", "show ans : "+jsonString);

下一步如何将此内容写入SD卡？

Answer 1

正如用户Zain所说，Gson使用起来更方便，但是，假设您从这一行获取Json字符串：

jsonString = mapper.writeValueAsString(listBook);

然后使用此方法将字符串写入sdcard中的文件。

public static void writeStringToFile(String p_string, String p_fileName)
    {
        FileOutputStream m_stream = null;
        try
        {
            m_stream = new FileOutputStream(p_fileName);
            m_stream.write(p_string.getBytes());
            m_stream.flush();
        }
        catch (Throwable m_th)
        {
            Log.e(TAG + " Error in writeStringToFile(String p_string, String p_fileName) of FileIO", m_th);
        }
        finally
        {
            if (m_stream != null)
            {
                try
                {
                    m_stream.close();
                }
                catch (Throwable m_e)
                {
                    Log.e(TAG + " Error in writeStringToFile(String p_string, String p_fileName) of FileIO", m_e);
                }
                m_stream = null;
            }
        }
    }