使用 clob 以 json 格式可视化 xml 内容的问题答案

【问题标题】：Problems visualizing the content of an xml in json format using clob使用 clob 以 json 格式可视化 xml 内容的问题
【发布时间】：2018-12-08 11:03:12
【问题描述】：

我正在测试查询表的代码，以 XML 格式获取结果，将其转换为 JSON 格式，并将其显示在屏幕上进行测试。我的问题是，当以 varchar 格式显示 JSON 时（使用 GetStringVal）它工作正常，但如果结果很广泛，我将其显示为 Clob（使用 GetClobVal）。在这种情况下，显示的字符串包括文字“& quot;”什么时候应该包括双引号。

接下来，我将向您展示用于将 xml 转换为 json 的函数，接下来是一个匿名块，其中包含在一个小 xml 上执行的测试。

我的数据库是 Oracle 12.1

感谢您有兴趣帮助我。

--Define a function with the XSLT to convert the XML to JSON
SET DEFINE OFF
  CREATE OR REPLACE 
  FUNCTION style_sheet_json 
  RETURN VARCHAR2 IS
    l_xslt VARCHAR2 ( 32000 );
  BEGIN
    l_xslt := '<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<!--
  Copyright (c) 2006, Doeke Zanstra
  All rights reserved.

  Redistribution and use in source and binary forms, with or without modification,
  are permitted provided that the following conditions are met:

  Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer. Redistributions in binary
  form must reproduce the above copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other materials provided with
  the distribution.

  Neither the name of the dzLib nor the names of its contributors may be used to
  endorse or promote products derived from this software without specific prior
  written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  THE POSSIBILITY OF SUCH DAMAGE.
-->

  <xsl:output indent="no" omit-xml-declaration="yes" method="text" encoding="UTF-8" media-type="text/x-json"/>
  <xsl:strip-space elements="*"/>
  <!--contant-->
  <xsl:variable name="d">0123456789</xsl:variable>

  <!-- ignore document text -->
  <xsl:template match="text()[preceding-sibling::node() or following-sibling::node()]"/>

  <!-- string -->
  <xsl:template match="text()">
    <xsl:call-template name="escape-string">
      <xsl:with-param name="s" select="."/>
    </xsl:call-template>
  </xsl:template>

  <!-- Main template for escaping strings; used by above template and for object-properties
       Responsibilities: placed quotes around string, and chain up to next filter, escape-bs-string -->
  <xsl:template name="escape-string">
    <xsl:param name="s"/>
    <xsl:text>"</xsl:text>
    <xsl:call-template name="escape-bs-string">
      <xsl:with-param name="s" select="$s"/>
    </xsl:call-template>
    <xsl:text>"</xsl:text>
  </xsl:template>

  <!-- Escape the backslash (\) before everything else. -->
  <xsl:template name="escape-bs-string">
    <xsl:param name="s"/>
    <xsl:choose>
      <xsl:when test="contains($s,''\'')">
        <xsl:call-template name="escape-quot-string">
          <xsl:with-param name="s" select="concat(substring-before($s,''\''),''\\'')"/>
        </xsl:call-template>
        <xsl:call-template name="escape-bs-string">
          <xsl:with-param name="s" select="substring-after($s,''\'')"/>
        </xsl:call-template>
      </xsl:when>
      <xsl:otherwise>
        <xsl:call-template name="escape-quot-string">
          <xsl:with-param name="s" select="$s"/>
        </xsl:call-template>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

  <!-- Escape the double quote ("). -->
  <xsl:template name="escape-quot-string">
    <xsl:param name="s"/>
    <xsl:choose>
      <xsl:when test="contains($s,'';'')">
        <xsl:call-template name="encode-string">
          <xsl:with-param name="s" select="concat(substring-before($s,'';''),''&quot;'')"/>
        </xsl:call-template>
        <xsl:call-template name="escape-quot-string">
          <xsl:with-param name="s" select="substring-after($s,'';'')"/>
        </xsl:call-template>
      </xsl:when>
      <xsl:otherwise>
        <xsl:call-template name="encode-string">
          <xsl:with-param name="s" select="$s"/>
        </xsl:call-template>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

  <!-- Replace tab, line feed and/or carriage return by its matching escape code. Can''t escape backslash
       or double quote here, because they don''t replace characters (; becomes \t), but they prefix
       characters (\ becomes \\). Besides, backslash should be seperate anyway, because it should be
       processed first. This function can''t do that. -->
  <xsl:template name="encode-string">
    <xsl:param name="s"/>
    <xsl:choose>
      <!-- tab -->
      <xsl:when test="contains($s,'';'')">
        <xsl:call-template name="encode-string">
          <xsl:with-param name="s" select="concat(substring-before($s,'';''),''\t'',substring-after($s,'';''))"/>
        </xsl:call-template>
      </xsl:when>
      <!-- line feed -->
      <xsl:when test="contains($s,'';'')">
        <xsl:call-template name="encode-string">
          <xsl:with-param name="s" select="concat(substring-before($s,'';''),''\n'',substring-after($s,'';''))"/>
        </xsl:call-template>
      </xsl:when>
      <!-- carriage return -->
      <xsl:when test="contains($s,'';'')">
        <xsl:call-template name="encode-string">
          <xsl:with-param name="s" select="concat(substring-before($s,'';''),''\r'',substring-after($s,'';''))"/>
        </xsl:call-template>
      </xsl:when>
      <xsl:otherwise><xsl:value-of select="$s"/></xsl:otherwise>
    </xsl:choose>
  </xsl:template>

  <!-- number (no support for javascript mantise) -->
  <xsl:template match="text()[not(string(number())=''NaN'')]">
    <xsl:value-of select="."/>
  </xsl:template>

  <!-- boolean, case-insensitive -->
  <xsl:template match="text()[translate(.,''TRUE'',''true'')=''true'']">true</xsl:template>
  <xsl:template match="text()[translate(.,''FALSE'',''false'')=''false'']">false</xsl:template>

  <!-- item:null -->
  <xsl:template match="*[count(child::node())=0]">
    <xsl:call-template name="escape-string">
      <xsl:with-param name="s" select="local-name()"/>
    </xsl:call-template>
    <xsl:text>:null</xsl:text>
    <xsl:if test="following-sibling::*">,</xsl:if>
    <xsl:if test="not(following-sibling::*)">}</xsl:if> <!-- MBR 30.01.2010: added this line as it appeared to be missing from stylesheet -->
  </xsl:template>

  <!-- object -->
  <xsl:template match="*" name="base">
    <xsl:if test="not(preceding-sibling::*)">{</xsl:if>
    <xsl:call-template name="escape-string">
      <xsl:with-param name="s" select="name()"/>
    </xsl:call-template>
    <xsl:text>:</xsl:text>
    <xsl:apply-templates select="child::node()"/>
    <xsl:if test="following-sibling::*">,</xsl:if>
    <xsl:if test="not(following-sibling::*)">}</xsl:if>
  </xsl:template>

  <!-- array -->
  <xsl:template match="*[count(../*[name(../*)=name(.)])=count(../*) and count(../*)&gt;1]">
    <xsl:if test="not(preceding-sibling::*)">[</xsl:if>
    <xsl:choose>
      <xsl:when test="not(child::node())">
        <xsl:text>null</xsl:text>
      </xsl:when>
      <xsl:otherwise>
        <xsl:apply-templates select="child::node()"/>
      </xsl:otherwise>
    </xsl:choose>
    <xsl:if test="following-sibling::*">,</xsl:if>
    <xsl:if test="not(following-sibling::*)">]</xsl:if>
  </xsl:template>

  <!-- convert root element to an anonymous container -->
  <xsl:template match="/">
    <xsl:apply-templates select="node()"/>
  </xsl:template>

</xsl:stylesheet>';

    RETURN ( l_xslt );

  END style_sheet_json;
/


DECLARE
l_xml XMLTYPE;
l_json XMLTYPE;
BEGIN

l_xml := XMLTYPE (
'<ROWSET>
 <ROW>
  <ID>4</ID>
  <DENOPAIS>Afganistán</DENOPAIS>
 </ROW>
</ROWSET>');

--Las 2 impresiones siguientes muestran lo mismo, el xml tal cual
dbms_output.put_line ( 'Shows xml as varchar');
dbms_output.put_line ( l_xml.GetStringVal());

dbms_output.put_line ('');
dbms_output.put_line ( 'Shows xml as clob');
dbms_output.put_line ( l_xml.GetClobVal());

dbms_output.put_line ('');
dbms_output.put_line ( 'Converting xml to json format...');
l_json := l_xml.TRANSFORM ( XMLTYPE ( style_sheet_json () ) );

dbms_output.put_line ('');
dbms_output.put_line ( 'Shows json as varchar');
dbms_output.put_line ( l_json.GetStringVal());

dbms_output.put_line ('');
dbms_output.put_line ( 'Shows json as clob');
dbms_output.put_line ( l_json.GetClobVal());

end;

【问题讨论】：

与您的问题完全不相关，但您可以使用dbms_output.new_line; 代替dbms_output.put_line ('');。当然，您可能更喜欢现在的方式。（也很好奇你为什么要通过 XML 并转换为 JSON，当12c supports JSON natively？）

标签： json plsql oracle12c clob

【解决方案1】：

不确定为什么会这样，可能有更好的方法来阻止它，但作为一种解决方法，您可以将 XML 序列化为 CLOB 变量；也不完全确定为什么会这样......

DECLARE
l_xml XMLTYPE;
l_json XMLTYPE;
l_clob CLOB;
BEGIN
...
dbms_output.put_line ('');
dbms_output.put_line ( 'Shows json as serialiaed clob');
select xmlserialize( content l_json as clob ) into l_clob from dual;
dbms_output.put_line ( l_clob );

end;
/

显示

...
Converting xml to json format...

Shows json as varchar
{"ROWSET":{"ROW":{"ID":4,"DENOPAIS":"Afganistán"}}}

Shows json as clob
{&quot;ROWSET&quot;:{&quot;ROW&quot;:{&quot;ID&quot;:4,&quot;DENOPAIS&quot;:&quot;Afganistán&quot;}}}

Shows json as serialiaed clob
{"ROWSET":{"ROW":{"ID":4,"DENOPAIS":"Afganistán"}}}

【讨论】：

【解决方案2】：

提供解决方案的用户表示他在几年前评论过这个问题here。

由于TRANSFORM方法返回的是一个XMLType的实例，所以当样式表的输出方法设置为文本时会出现一些差异。

在这种情况下正确的行为是什么？不要转义字符实体以显示为明文，或保持原样以使 XML 内容保持有效。

引用的出版物中提到的解决方法适用于 Oracle 11.2，并且在 12c 中该行为似乎发生了一些变化。

即便如此，也可以使用类似的方法来获得预期的 CLOB 输出：

DECLARE    
  l_xsl    xmltype := xmltype(style_sheet_json);  
  l_xml    xmltype;  
  l_json   xmltype;  
  l_out    clob;  

BEGIN  
  l_xml := XMLTYPE (  
'<ROWSET>  
<ROW>  
  <ID>4</ID>  
  <DENOPAIS>Afganistán</DENOPAIS>  
</ROW>  
</ROWSET>');  

  dbms_output.put_line('Using explicit conversion of character entities :');  
  l_json := l_xml.transform(l_xsl);  
  l_out := dbms_xmlgen.convert(l_json.getclobval(), dbms_xmlgen.ENTITY_DECODE);  
  dbms_output.put_line(l_out);  

  dbms_output.new_line;  
  dbms_output.put_line('Using SQL function XMLTransform :');  
  select xmltransform(l_xml, l_xsl)  
  into l_json  
  from dual;                

  l_out := l_json.getclobval;                
  dbms_output.put_line(l_out);                

  dbms_output.new_line;                
  dbms_output.put_line('Using SQL functions XMLTransform and XMLCast :');  
  select xmlcast(xmltransform(l_xml, l_xsl) as clob)   
  into l_out                
  from dual;                

  dbms_output.put_line(l_out);                

END;                
/                

Using explicit conversion of character entities :      
{"ROWSET":{"ROW":{"ID":4,"DENOPAIS":"Afganistán"}}}    

Using SQL function XMLTransform :                
{"ROWSET":{"ROW":{"ID":4,"DENOPAIS":"Afganistán"}}}    

Using SQL functions XMLTransform and XMLCast :         
{"ROWSET":{"ROW":{"ID":4,"DENOPAIS":"Afganistán"}}}    

PL/SQL procedure successfully completed.

【讨论】：