用于 XML 到 JSON 到 XML 阻抗不匹配的 Java 库

Question

我需要使用 Java 将 XML 无损转换为 JSON，然后再返回。我使用了一个名为 jsonxml 的 Javascript 库，它可以正常运行，但在 Java 中没有。

我似乎找到了最好的 JSON-java，它在 Stack Overflow 中经常被提及，但它在太多方面都未能通过测试。

这是我的测试用例代码...

//---------------------------------------------------
import org.json.*;
//---------------------------------------------------
public class rjx
    {
    //-----------------------------------------------
    private String j2x(String json)
        {
        return(XML.toString(new JSONObject(json)));
        }
    //-----------------------------------------------
    private String x2j(String xml)
        {
        return(XML.toJSONObject(xml).toString());
        }
    //-----------------------------------------------
    //-----------------------------------------------
    public static void main(String[] args)
        {
        //-------------------------------------------
        rjx o = new rjx();
        //-------------------------------------------
        try
            {
            String xml = new String();
            String reversed = new String();
            System.out.println("=======");
            xml = "<e/>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e>text</e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e name='value' />";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e name='value'>text</e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><a>text</a><b>text</b></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><a>text</a><a>text</a></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e>text<a>text</a></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<a>hello</a>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<a x='y'>hello</a>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<a id='a'><b id='b'>hey!</b></a>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<a>x<c/>y</a>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<x u=''/>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<html><head><title>Xml/Json</title><meta name='x' content='y' /></head><body></body></html>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<ol class='xoxo'><li>Subject 1<ol><li>subpoint a</li><li>subpoint b</li></ol></li><li><span>Subject 2</span><ol compact='compact'><li>subpoint c</li><li>subpoint d</li></ol></li></ol>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<span class='vevent'><a class='url' href='http://www.web2con.com/'><span class='summary'>Web 2.0 Conference</span><abbr class='dtstart' title='2005-10-05'>October 5</abbr><abbr class='dtend' title='2005-10-08'>7</abbr><span class='location'>Argent Hotel, San Francisco, CA</span></a></span>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><![CDATA[ .. some data .. ]]></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><a /><![CDATA[ .. some data .. ]]><b /></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e>some text<![CDATA[ .. some data .. ]]>more text</e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e>some text<![CDATA[ .. some data .. ]]><a /></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><![CDATA[ .. some data .. ]]><![CDATA[ .. more data .. ]]></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><![CDATA[ .. some data .. ]]><![CDATA[ .. & more data .. ]]></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("-------");
            xml = "<e><![CDATA[ .. some data .. ]]><![PCDATA[ .. &amp; still more data .. ]]></e>";
            System.out.println(xml);
            reversed = o.j2x(o.x2j(xml));
            System.out.println(reversed);
            if (xml.equals(reversed))
                System.out.println("PASS");
            else
                System.out.println("FAIL");
            System.out.println("=======");
            }
        catch (Exception e)
            {
            System.err.println("error: rjx.main>>" + e.toString());
            System.exit(1);
            }
        System.exit(0);
        }
    //-----------------------------------------------
    }
//---------------------------------------------------

结果……

=======
<e/>
<e/>
PASS
-------
<e>text</e>
<e>text</e>
PASS
-------
<e name='value' />
<e><name>value</name></e>
FAIL
-------
<e name='value'>text</e>
<e><name>value</name>text</e>
FAIL
-------
<e><a>text</a><b>text</b></e>
<e><a>text</a><b>text</b></e>
PASS
-------
<e><a>text</a><a>text</a></e>
<e><a>text</a><a>text</a></e>
PASS
-------
<e>text<a>text</a></e>
<e><a>text</a>text</e>
FAIL
-------
<a>hello</a>
<a>hello</a>
PASS
-------
<a x='y'>hello</a>
<a><x>y</x>hello</a>
FAIL
-------
<a id='a'><b id='b'>hey!</b></a>
<a><b><id>b</id>hey!</b><id>a</id></a>
FAIL
-------
<a>x<c/>y</a>
<a><c/>x
y</a>
FAIL
-------
<x u=''/>
<x><u/></x>
FAIL
-------
<html><head><title>Xml/Json</title><meta name='x' content='y' /></head><body></body></html>
<html><head><meta><name>x</name>y</meta><title>Xml/Json</title></head><body/></html>
FAIL
-------
<ol class='xoxo'><li>Subject 1<ol><li>subpoint a</li><li>subpoint b</li></ol></li><li><span>Subject 2</span><ol compact='compact'><li>subpoint c</li><li>subpoint d</li></ol></li></ol>
<ol><class>xoxo</class><li><ol><li>subpoint a</li><li>subpoint b</li></ol>Subject 1</li><li><ol><compact>compact</compact><li>subpoint c</li><li>subpoint d</li></ol><span>Subject 2</span></li></ol>
FAIL
-------
<span class='vevent'><a class='url' href='http://www.web2con.com/'><span class='summary'>Web 2.0 Conference</span><abbr class='dtstart' title='2005-10-05'>October 5</abbr><abbr class='dtend' title='2005-10-08'>7</abbr><span class='location'>Argent Hotel, San Francisco, CA</span></a></span>
<span><a><href>http://www.web2con.com/</href><abbr><title>2005-10-05</title><class>dtstart</class>October 5</abbr><abbr><title>2005-10-08</title><class>dtend</class>7</abbr><class>url</class><span><class>summary</class>Web 2.0 Conference</span><span><class>location</class>Argent Hotel, San Francisco, CA</span></a><class>vevent</class></span>
FAIL
-------
<e><![CDATA[ .. some data .. ]]></e>
<e> .. some data .. </e>
FAIL
-------
<e><a /><![CDATA[ .. some data .. ]]><b /></e>
<e><a/><b/> .. some data .. </e>
FAIL
-------
<e>some text<![CDATA[ .. some data .. ]]>more text</e>
<e><array>some text</array><array> .. some data .. </array><array>more text</array></e>
FAIL
-------
<e>some text<![CDATA[ .. some data .. ]]><a /></e>
<e><a/>some text
 .. some data .. </e>
FAIL
-------
<e><![CDATA[ .. some data .. ]]><![CDATA[ .. more data .. ]]></e>
<e><array> .. some data .. </array><array> .. more data .. </array></e>
FAIL
-------
<e><![CDATA[ .. some data .. ]]><![CDATA[ .. & more data .. ]]></e>
<e><array> .. some data .. </array><array> .. &amp; more data .. </array></e>
FAIL
-------
<e><![CDATA[ .. some data .. ]]><![PCDATA[ .. &amp; still more data .. ]]></e>
error: rjx.main>>org.json.JSONException: Expected 'CDATA[' at 41 [character 42 line 1]

是否有可以通过所有测试的库，也许是 JSON-java 的一个分支？

顺便说一句，我可以原谅订单不匹配的失败，这在我的规范范围内，但结构更改不是。

Answer 1

这取决于您的具体要求。

例如，如果你看到

<p id="foo" class='  x  '>Hello, <i>cruel</i> world.</p   >

如果你得到以下回报，它是否算“无损”？

<p class='x' id='foo'>, <i>cruel</i> world.</p>

如果这不算作无损，那么除了在 XML 中转义和引号并将整个事物称为一个 JSON 字符串之外，进行无损往返将非常困难。这当然很简单，但 JSON 对里面的内容一无所知。

几乎所有 XML 解析器都会丢弃标签内的空白差异；这是设计的行为。有些还返回属性而不考虑顺序。到 JSON 的现成转换可能会将属性放入 JSON 哈希，之后它们的原始顺序肯定会消失，因此无法恢复。还有一些其他问题，例如“nbsp;”是否== " " == " ".... 使用“Canonical XML”（参见https://www.w3.org/TR/xml-c14n11/）将有助于避免此类问题。

不过，我有点困惑，因为我想不出没有可用的 XML 解析器的环境。为什么不进行任何转换，只在目的地解析 XML？听起来好像目的地没有改变数据，因为如果它确实往返显然根本不起作用。如果您发送 XML，目的地更容易验证它以确保它正常。

另一方面，如果上面的示例确实对您而言算作“无损”，那么事情就会变得容易得多。因为 XML 元素具有重要的 names 和 order，您必须保留它们，所以无论您使用什么，都应该为每个元素创建一个 JSON 数组和一个 JSON 哈希。也许最简单的是：

[ { "#":"p" "id":""foo"" "class":""x"" },
    "Hello, ",
    [ { "#":"i" },
        "cruel"
    ], 
    "world."
]

我不知道有什么 Javascript 或 Java 库可以做到这一点或等效。我有 Python，但是在这里粘贴有点大。您可以通过以下方式非常接近：

sed -E \
-e 's@>([^<]+)@>"\1"<@g' \ 
-e 's@<([^\s/>]+)(\s+[^>]*)?/>@[{"#":"\1", \2}],@g' \ 
-e 's@<([^\s/>]+)(\s+[^>]*)?>@[{"#":"\1", \2},@g' \
-e 's@<\?(\w+)(\s+([^?]|\?[^>])*)?\?>@[{"#":"#PI", "#target":"\1", \2]}@g' \ 
-e 's@<!--(([^-]|-[^-]|--[^>])*)-->@/* \1 */@g' \ 
-e 's@\s+(\w+)\s*=\s*("[^"]*")@ "\1":"\2",@g' \ 
-e 's@</([^\s/>]+)\s*>@],@g' \ 
-e 's@&#[xX]([0-9a-fA-F]+);@\\u{\1}@g' \ 
-e 's@&lt;@<@g' \ 
-e 's@&gt;@>@g' \ 
-e 's@&amp;@&@g' \ 
-e 's@&lsqb;@[@g' \ 
-e 's@&rsqb;@]@g' \ 
-e 's@"\s*([-+]?\d+(\.\d+)?([eE][-+?]\d+)?)\s*"@\1@g'