Gson Unicode字符转换为Unicode字符代码

Z时代
2024-01-10
分类：问答

在下面查看我的代码。我有一个包含Unicode字符代码的JSON字符串。我将其转换为Java对象，然后将其转换回JSON字符串。但是，您可以看到输入和输出JSON字符串不匹配。是否可以使用Gson将我的对象转换为原始JSON字符串？我想outputJson和一样inputJson。

static class Book {
    String description;
}
public static void test() {
    Gson gson = new Gson();
    String inputJson = "{\"description\":\"Tikrovi\\u0161kai para\\u0161ytas k\\u016brinys\"}";
    Book book = gson.fromJson(inputJson, Book.class);
    String outputJson = gson.toJson(book);
    System.out.println(inputJson);
    System.out.println(outputJson);
    // Prints:
    // {"description":"Tikrovi\u0161kai para\u0161ytas k\u016brinys"}
    // {"description":"Tikroviškai parašytas kūrinys"}
}

回答：

不幸的是，Gson似乎不支持它。所有JSON输入/输出分别集中在Gson（从2.8.0开始）JsonReader和JsonWriter。JsonReader可以使用其私有readEscapeCharacter方法读取Unicode转义。但是，与有所不同的是JsonReader，JsonWriter只需将字符串写入后备Writer实例，除了\u2028和以外，不对127以上的字符进行字符校正\u2029。可能唯一可以做的是编写自定义转义符，Writer以便发出Unicode转义。

final class EscapedWriter
        extends Writer {
    private static final char[] hex = {
            '0', '1', '2', '3',
            '4', '5', '6', '7',
            '8', '9', 'a', 'b',
            'c', 'd', 'e', 'f'
    };
    private final Writer writer;
    // I/O components are usually implemented in not thread-safe manner
    // so we can save some time on constructing a single UTF-16 escape
    private final char[] escape = { '\\', 'u', 0, 0, 0, 0 };
    EscapedWriter(final Writer writer) {
        this.writer = writer;
    }
    // This implementation is not very efficient and is open for enhancements:
    // * constructing a single "normalized" buffer character array so that it could be passed to the downstream writer
    //   rather than writing characters one by one
    // * etc...
    @Override
    public void write(final char[] buffer, final int offset, final int length)
            throws IOException {
        for ( int i = offset; i < length; i++ ) {
            final int ch = buffer[i];
            if ( ch < 128 ) {
                writer.write(ch);
            } else {
                escape[2] = hex[(ch & 0xF000) >> 12];
                escape[3] = hex[(ch & 0x0F00) >> 8];
                escape[4] = hex[(ch & 0x00F0) >> 4];
                escape[5] = hex[ch & 0x000F];
                writer.write(escape);
            }
        }
    }
    @Override
    public void flush()
            throws IOException {
        writer.flush();
    }
    @Override
    public void close()
            throws IOException {
        writer.close();
    }
    // Some java.io.Writer subclasses may use java.lang.Object.toString() to materialize their accumulated state by design
    // so it has to be overridden and forwarded as well
    @Override
    public String toString() {
        return writer.toString();
    }
}

该作家未经充分测试，不尊重\u2028和\u2029。然后只需在调用toJson方法时配置输出目标即可：

final String input = "{\"description\":\"Tikrovi\\u0161kai para\\u0161ytas k\\u016brinys\"}";
final Book book = gson.fromJson(input, Book.class);
final Writer output = new EscapedWriter(new StringWriter());
gson.toJson(book, output);
System.out.println(input);
System.out.println(output);

输出：