向 Jackson XML 序列化添加獨立指令

Question

我試圖讓 Jackson 像 JAXB 一樣生成 XML 標頭，但我不知道如何添加“standalone='yes'？”

例子：

public class XmlTest {

    @XmlRootElement
    public static class Book {

    }

    @Test
    public void testBookXml() throws JsonProcessingException {
        XmlMapper mapper = new XmlMapper();
        mapper.configure(ToXmlGenerator.Feature.WRITE_XML_DECLARATION, true);

        System.out.println("Jackson\n" + mapper.writeValueAsString(new Book()) + "\n");

        StringWriter sw = new StringWriter();
        JAXB.marshal(new Book(), sw);
        System.out.println("JAXB\n" + sw.toString());
    }
}

輸出是這樣的：

Jackson
<?xml version='1.0' encoding='UTF-8'?><Book/>

JAXB
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<book/>

我不在乎<Book/> vs <book/> 。 除了字符串操作之外，有沒有辦法讓 Jackson 標頭像 JAXB 一樣？

Answer 1

我遇到了同樣的問題，我通過重新加載類BufferingXmlWriter （從源代碼復制並修改方法）解決了這個問題，在使用 Jackson 生成 XML 之前必須重新加載

1. 創建包 com.ctc.wstx.sw 並創建類BufferingXmlWriter
2. 從真實的com.ctc.wstx.sw.BufferingXmlWriter復制源代碼
3. 修改方法writeXmlDeclaration(String version, String encoding, String standalone)

public void writeXmlDeclaration(String version, String encoding, String standalone)
            throws IOException
 {
       // final char chQuote = (mUseDoubleQuotesInXmlDecl ? '"' : '\'');
        final char chQuote = '"';
    
        fastWriteRaw("<?xml version=");
        fastWriteRaw(chQuote);
        fastWriteRaw(version);
        fastWriteRaw(chQuote);
    
        if (encoding != null && encoding.length() > 0) {
            fastWriteRaw(" encoding=");
            fastWriteRaw(chQuote);
            fastWriteRaw(encoding);
            fastWriteRaw(chQuote);
        }
        if (standalone == null) {
            fastWriteRaw(" standalone=");
            fastWriteRaw(chQuote);
            fastWriteRaw("yes");
            fastWriteRaw(chQuote);
        }
        fastWriteRaw('?', '>');
 }    

4. 重新加載

    Class.forName("com.ctc.wstx.sw.BufferingXmlWriter");

5. 結果

   <?xml version="1.0" encoding="UTF-8" standalone="yes"?>