目前我们有几个查询，我们从数据库获取数据并将其存储在内存中。现在，对于相同的查询，我们需要一种从 xml 而不是数据库服务器获取数据的方法，即数据将以以下形式保存在 xml 中:
<?xml version='1.0' encoding='Cp1252' ?>
<tables>
<TableOne>
<Row1>
<Column1>TableOne Row1 Column1 Value</Column1>
<Column2>TableOne Row1 Column2 Value</Column2>
<Column3>TableOne Row1 Column3 Value</Column3>
</Row1>
<Row2>
<Column1>TableOne Row2 Column1 Value</Column1>
<Column2>TableOne Row2 Column2 Value</Column2>
<Column3>TableOne Row2 Column3 Value</Column3>
</Row2>
</TableOne>
<TableTwo>
<TableTwoRow1>
<TableTwoRow1Column1>TableOne Row1 Column1 Value</TableTwoRow1Column1>
<TableTwoRow1Column2>TableTwoRow1 Column2 Value</TableTwoRow1Column2>
<TableTwoRow1Column3>TableTwoRow1 Column3 Value</TableTwoRow1Column3>
</TableTwoRow1>
<TableTwoRow2>
<TableTwoRow2Column1>TableTwoRow2 Column1 Value</TableTwoRow2Column1>
<TableTwoRow2Column2>TableTwoRow2 Column2 Value</TableTwoRow2Column2>
<TableTwoRow2Column3>TableTwoRow2 Column3 Value</TableTwoRow2Column3>
</TableTwoRow2>
</TableTwo>
</tables>
为了实现上述功能，我制作了自己的数据结构来存储上述 xml:
public class DataObject {
Map<String, Table> tables = new HashMap<String, Table>();
public Map<String, Table> getTables() {
return tables;
}
public void setTable(Map<String, Table> table) {
this.tables = table;
}
}
然后表格将如下所示:
public class Table {
private String tableName;
private List<Map<String,String>> rowList = new ArrayList<Map<String,String>>();
public Table(String tableName) {
super();
this.tableName = tableName;
}
public List<Map<String, String>> getRowList() {
return rowList;
}
public void setRowList(List<Map<String, String>> rowList) {
this.rowList = rowList;
}
public String getTableName() {
return tableName;
}
public void setTableName(String tableName) {
this.tableName = tableName;
}
}
每一行将表示为 Map，多行将表示为 List。我已经能够将数据从 xml 传递到上面的“DataObject”，如下所示:
私有(private)DataObject getDataObject(文档文档){
DataObject dataObject = new DataObject();
Element rootElement = document.getRootElement();
List<Element> tableList = rootElement.getChildren();
for (Element tableElement : tableList) {
String tableName = tableElement.getName();
Table table = new Table(tableName);
dataObject.getTables().put(tableName, table);
List<Element> rows = tableElement.getChildren();
for (Element rowElement : rows) {
Map<String, String> row = new HashMap<String, String>();
List<Element> columns = rowElement.getChildren();
for (Element columnElement : columns) {
String columnName = columnElement.getName();
String columnValue = columnElement.getValue();
row.put(columnName, columnValue);
}
table.getRowList().add(row);
}
}
return dataObject;
}
现在我想不出一种有效的方法来查询上述 dataObject 来执行查询，而且我找不到任何内置 API 可以帮助我做到这一点。查询将具有 select、group by、order by 和所有逻辑运算符。 任何想法都将不胜感激。
最佳答案
为什么是 SQL？考虑另一种专门为 XML 设计的专用声明性语言:XSLT 。 Java 附带了 XSLT 1.0 处理器以及 XSLT 2.0 和 3.0 的外部处理器，包括 Xalan and Saxon在Java中运行。在 XSLT 中，您可以找到大多数 SQL 对应项，因为文档可以根据 XPath 表达式、模板处理以及基本逻辑和算术运算进行转换。请注意，XSLT 脚本是格式正确的 XML 文件(带有特殊说明)!
下面是一个使用截至 2015 年 8 月一周前 20 位 Stackoverflow 用户的示例。示例显示了 XSLT 中的对应 SQL。在此示例中，topusers 是表，其子项是列。我们的好 friend @JB Nizet 上面的评论已包含在 XML 中!
XML来源
<?xml version='1.0' encoding='UTF-8'?>
<stackoverflow>
<topusers>
<user>Gordon Linoff</user>
<link>https://stackoverflow.com/users/1144035/gordon-linoff</link>
<goldbadges>18</goldbadges>
<silverbadges>81</silverbadges>
<bronzebadges>134</bronzebadges>
<membership>3 years, 6 months</membership>
<yearRank>#1</yearRank>
<totalReputation>320356</totalReputation>
<yearReputation>72008</yearReputation>
<topskill>sql</topskill>
</topusers>
<topusers>
<user>Martijn Pieters</user>
<link>https://stackoverflow.com/users/100297/martijn-pieters</link>
<goldbadges>36</goldbadges>
<silverbadges>787</silverbadges>
<bronzebadges>975</bronzebadges>
<membership>6 years, 3 months</membership>
<yearRank>#2</yearRank>
<totalReputation>385697</totalReputation>
<yearReputation>66886</yearReputation>
<topskill>python</topskill>
</topusers>
<topusers>
<user>anubhava</user>
<link>https://stackoverflow.com/users/548225/anubhava</link>
<goldbadges>25</goldbadges>
<silverbadges>100</silverbadges>
<bronzebadges>173</bronzebadges>
<membership>4 years, 7 months</membership>
<yearRank>#3</yearRank>
<totalReputation>279930</totalReputation>
<yearReputation>62759</yearReputation>
<topskill>regex</topskill>
</topusers>
<topusers>
<user>Jon Skeet</user>
<link>https://stackoverflow.com/users/22656/jon-skeet</link>
<goldbadges>379</goldbadges>
<silverbadges>5537</silverbadges>
<bronzebadges>6720</bronzebadges>
<membership>6 years, 10 months</membership>
<yearRank>#4</yearRank>
<totalReputation>797069</totalReputation>
<yearReputation>57963</yearReputation>
<topskill>c#</topskill>
</topusers>
<topusers>
<user>akrun</user>
<link>https://stackoverflow.com/users/3732271/akrun</link>
<goldbadges>5</goldbadges>
<silverbadges>25</silverbadges>
<bronzebadges>58</bronzebadges>
<membership>1 year, 1 month</membership>
<yearRank>#5</yearRank>
<totalReputation>88928</totalReputation>
<yearReputation>57384</yearReputation>
<topskill>r</topskill>
</topusers>
<topusers>
<user>VonC</user>
<link>https://stackoverflow.com/users/6309/vonc</link>
<goldbadges>131</goldbadges>
<silverbadges>1354</silverbadges>
<bronzebadges>1447</bronzebadges>
<membership>6 years, 10 months</membership>
<yearRank>#6</yearRank>
<totalReputation>512007</totalReputation>
<yearReputation>56260</yearReputation>
<topskill>git</topskill>
</topusers>
<topusers>
<user>CommonsWare</user>
<link>https://stackoverflow.com/users/115145/commonsware</link>
<goldbadges>53</goldbadges>
<silverbadges>1104</silverbadges>
<bronzebadges>1155</bronzebadges>
<membership>6 years, 2 months</membership>
<yearRank>#7</yearRank>
<totalReputation>487584</totalReputation>
<yearReputation>54921</yearReputation>
<topskill>android</topskill>
</topusers>
<topusers>
<user>T.J. Crowder</user>
<link>https://stackoverflow.com/users/157247/t-j-crowder</link>
<goldbadges>51</goldbadges>
<silverbadges>556</silverbadges>
<bronzebadges>692</bronzebadges>
<membership>5 years, 11 months</membership>
<yearRank>#8</yearRank>
<totalReputation>374425</totalReputation>
<yearReputation>54121</yearReputation>
<topskill>javascript</topskill>
</topusers>
<topusers>
<user>Hans Passant</user>
<link>https://stackoverflow.com/users/17034/hans-passant</link>
<goldbadges>62</goldbadges>
<silverbadges>679</silverbadges>
<bronzebadges>1277</bronzebadges>
<membership>6 years, 10 months</membership>
<yearRank>#9</yearRank>
<totalReputation>565002</totalReputation>
<yearReputation>53886</yearReputation>
<topskill>c#</topskill>
</topusers>
<topusers>
<user>BalusC</user>
<link>https://stackoverflow.com/users/157882/balusc</link>
<goldbadges>148</goldbadges>
<silverbadges>1925</silverbadges>
<bronzebadges>2235</bronzebadges>
<membership>5 years, 11 months</membership>
<yearRank>#10</yearRank>
<totalReputation>584857</totalReputation>
<yearReputation>53693</yearReputation>
<topskill>java</topskill>
</topusers>
<topusers>
<user>dasblinkenlight</user>
<link>https://stackoverflow.com/users/335858/dasblinkenlight</link>
<goldbadges>31</goldbadges>
<silverbadges>342</silverbadges>
<bronzebadges>617</bronzebadges>
<membership>5 years, 3 months</membership>
<yearRank>#11</yearRank>
<totalReputation>354707</totalReputation>
<yearReputation>52779</yearReputation>
<topskill>java</topskill>
</topusers>
<topusers>
<user>Eran</user>
<link>https://stackoverflow.com/users/1221571/eran</link>
<goldbadges>18</goldbadges>
<silverbadges>114</silverbadges>
<bronzebadges>187</bronzebadges>
<membership>3 years, 5 months</membership>
<yearRank>#12</yearRank>
<totalReputation>105090</totalReputation>
<yearReputation>49529</yearReputation>
<topskill>java</topskill>
</topusers>
<topusers>
<user>Avinash Raj</user>
<link>https://stackoverflow.com/users/3297613/avinash-raj</link>
<goldbadges>6</goldbadges>
<silverbadges>25</silverbadges>
<bronzebadges>59</bronzebadges>
<membership>1 year, 5 months</membership>
<yearRank>#13</yearRank>
<totalReputation>96627</totalReputation>
<yearReputation>48928</yearReputation>
<topskill>regex</topskill>
</topusers>
<topusers>
<user>Arun P Johny</user>
<link>https://stackoverflow.com/users/114251/arun-p-johny</link>
<goldbadges>30</goldbadges>
<silverbadges>194</silverbadges>
<bronzebadges>254</bronzebadges>
<membership>6 years, 2 months</membership>
<yearRank>#14</yearRank>
<totalReputation>218919</totalReputation>
<yearReputation>45858</yearReputation>
<topskill>jquery</topskill>
</topusers>
<topusers>
<user>Alex Martelli</user>
<link>https://stackoverflow.com/users/95810/alex-martelli</link>
<goldbadges>64</goldbadges>
<silverbadges>752</silverbadges>
<bronzebadges>1056</bronzebadges>
<membership>6 years, 3 months</membership>
<yearRank>#15</yearRank>
<totalReputation>402886</totalReputation>
<yearReputation>44772</yearReputation>
<topskill>python</topskill>
</topusers>
<topusers>
<user>unutbu</user>
<link>https://stackoverflow.com/users/190597/unutbu</link>
<goldbadges>28</goldbadges>
<silverbadges>473</silverbadges>
<bronzebadges>617</bronzebadges>
<membership>5 years, 9 months</membership>
<yearRank>#16</yearRank>
<totalReputation>295951</totalReputation>
<yearReputation>44389</yearReputation>
<topskill>python</topskill>
</topusers>
<topusers>
<user>JB Nizet</user>
<link>https://stackoverflow.com/users/571407/jb-nizet</link>
<goldbadges>22</goldbadges>
<silverbadges>307</silverbadges>
<bronzebadges>491</bronzebadges>
<membership>4 years, 6 months</membership>
<yearRank>#17</yearRank>
<totalReputation>319659</totalReputation>
<yearReputation>43697</yearReputation>
<topskill>java</topskill>
</topusers>
<topusers>
<user>Quentin</user>
<link>https://stackoverflow.com/users/19068/quentin</link>
<goldbadges>42</goldbadges>
<silverbadges>491</silverbadges>
<bronzebadges>664</bronzebadges>
<membership>6 years, 10 months</membership>
<yearRank>#18</yearRank>
<totalReputation>397762</totalReputation>
<yearReputation>43626</yearReputation>
<topskill>javascript</topskill>
</topusers>
<topusers>
<user>Darin Dimitrov</user>
<link>https://stackoverflow.com/users/29407/darin-dimitrov</link>
<goldbadges>108</goldbadges>
<silverbadges>2089</silverbadges>
<bronzebadges>2107</bronzebadges>
<membership>6 years, 9 months</membership>
<yearRank>#19</yearRank>
<totalReputation>604319</totalReputation>
<yearReputation>43621</yearReputation>
<topskill>c#</topskill>
</topusers>
<topusers>
<user>alecxe</user>
<link>https://stackoverflow.com/users/771848/alecxe</link>
<goldbadges>19</goldbadges>
<silverbadges>108</silverbadges>
<bronzebadges>194</bronzebadges>
<membership>4 years, 2 months</membership>
<yearRank>#20</yearRank>
<totalReputation>116413</totalReputation>
<yearReputation>42215</yearReputation>
<topskill>python</topskill>
</topusers>
</stackoverflow>
SELECT 语句
SELECT User, Membership, Link
FROM topusers
WHERE topskill = 'Java'
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>
<xsl:template match="/stackoverflow">
<xsl:copy>
<xsl:apply-templates select="topusers[topskill='java']"/>
</xsl:copy>
</xsl:template>
<xsl:template match="topusers">
<xsl:copy>
<xsl:copy-of select="user"/>
<xsl:copy-of select="membership"/>
<xsl:copy-of select="link"/>
</xsl:copy>
</xsl:template>
</xsl:transform>
分组依据
SELECT topskill AS skill, SUM(goldbadges) AS SumOfGoldBadges,
SUM(silverbadges) AS SumOfSilverBadges, SUM(bronzebadges) AS SumOfBronzeBadges,
AVG(totalReputation) AS AvgOfReps,
Min(yearReputation) As MinOfYrReps, Max(yearReputation) As MaxOfYrReps
FROM topUsers
GROUP BY topskill
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
xmlns:exsl="http://exslt.org/common" extension-element-prefixes="exsl">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>
<xsl:key name="skillkey" match="topusers" use="topskill" />
<xsl:template match="/stackoverflow">
<xsl:copy>
<xsl:apply-templates select="topusers[generate-id() = generate-id(key('skillkey', topskill)[1])]"/>
</xsl:copy>
</xsl:template>
<!-- Muenchian Method -->
<xsl:template match="topusers">
<xsl:variable name="curr-group" select="key('skillkey', topskill)" />
<skill_group>
<skill><xsl:value-of select="$curr-group/topskill"/></skill>
<SumOfGoldBadges><xsl:value-of select="sum($curr-group/goldbadges)"/></SumOfGoldBadges>
<SumOfSilverBadges><xsl:value-of select="sum($curr-group/silverbadges)"/></SumOfSilverBadges>
<SumOfBronzeBadges><xsl:value-of select="sum($curr-group/bronzebadges)"/></SumOfBronzeBadges>
<AvgOfReps><xsl:value-of select="sum($curr-group/totalReputation)
div count($curr-group/totalReputation)"/></AvgOfReps>
<xsl:variable name="repsSorted">
<xsl:for-each select="$curr-group">
<xsl:sort select="yearReputation" data-type="number" order="ascending"/>
<xsl:copy-of select="yearReputation"/>
</xsl:for-each>
</xsl:variable>
<xsl:variable name="repsSortedSet" select="exsl:node-set($repsSorted)/yearReputation" />
<MinOfYrReps><xsl:value-of select="$repsSortedSet[1]"/></MinOfYrReps>
<MaxOfYrReps><xsl:value-of select="$repsSortedSet[last()]"/></MaxOfYrReps>
</skill_group>
</xsl:template>
</xsl:transform>
排序依据
SELECT * FROM topusers
ORDER BY goldbages DESC
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>
<!-- Identity Transform -->
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="stackoverflow">
<xsl:copy>
<xsl:apply-templates select="topusers">
<xsl:sort select="goldbadges" order="descending" data-type="number"/>
</xsl:apply-templates>
</xsl:copy>
</xsl:template>
</xsl:transform>
案例/时间
SELECT user, membership, link,
CASE
WHEN membership LIKE '%1 year%' OR membership LIKE '%2 years%'
OR membership LIKE '%3 years%'
THEN 'recent member'
WHEN membership LIKE '%4 years%' OR membership LIKE '%5 years%'
THEN 'mid member'
ELSE 'long member'
END AS member_type
FROM topusers
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>
<xsl:template match="/stackoverflow">
<xsl:copy>
<xsl:apply-templates select="topusers"/>
</xsl:copy>
</xsl:template>
<xsl:template match="topusers">
<xsl:copy>
<xsl:choose>
<xsl:when test="contains(membership, '1 year') or contains(membership, '2 years')
or contains(membership, '3 years')">
<xsl:copy-of select="user"/>
<xsl:copy-of select="membership"/>
<xsl:copy-of select="link"/>
<member_type>recent member</member_type>
</xsl:when>
<xsl:when test="contains(membership, '4 years') or contains(membership, '5 years')">
<xsl:copy-of select="user"/>
<xsl:copy-of select="membership"/>
<xsl:copy-of select="link"/>
<member_type>mid member</member_type>
</xsl:when>
<xsl:otherwise>
<xsl:copy-of select="user"/>
<xsl:copy-of select="membership"/>
<xsl:copy-of select="link"/>
<member_type>long member</member_type>
</xsl:otherwise>
</xsl:choose>
</xsl:copy>
</xsl:template>
</xsl:transform>
Java (在 XML 源上运行 XSLT 脚本)
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.*;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerException;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import javax.xml.transform.OutputKeys;
import java.io.*;
import java.io.File;
import java.io.IOException;
import java.net.URISyntaxException;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;
public class CourseList {
public static void main(String[] args) throws IOException, URISyntaxException,
SAXException, ParserConfigurationException,
TransformerException {
// Load XML and XSL Document
String inputXML = "/path/to/Input.xml";
String xslFile = "/path/to/XSLT/Script.xsl";
String outputXML = "/path/to/Output.xml";
Source xslt = new StreamSource(new File(xslFile));
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.parse (new File(inputXML));
// XSLT Transformation with pretty print
TransformerFactory prettyPrint = TransformerFactory.newInstance();
Transformer transformer = prettyPrint.newTransformer(xslt);
// Dynamic XSLT
String root = "stackoverflow";
String TableName = "topusers";
String Column1 = "user";
String Column2 = "membership";
String Column3 = "link";
String Column4 = "topskill";
String wherevalue = "java";
String xslStr = String.join("\n",
"<xsl:transform xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" version=\"1.0\">",
"<xsl:output version=\"1.0\" encoding=\"UTF-8\" indent=\"yes\" />",
"<xsl:strip-space elements=\"*\"/> ",
" <xsl:template match=\"/"+root+"\">",
" <xsl:copy>",
" <xsl:apply-templates select=\""+TableName+"["+Column4+"='"+wherevalue+"']\"/>",
" </xsl:copy>",
" </xsl:template>",
" <xsl:template match=\""+TableName+"\">",
" <xsl:copy>",
" <xsl:copy-of select=\""+Column1+"\"/>",
" <xsl:copy-of select=\""+Column2+"\"/>",
" <xsl:copy-of select=\""+Column3+"\"/>",
" </xsl:copy>",
" </xsl:template>",
"</xsl:transform>");
// Parse XSLT String and Configure Transformer
Source xslt = new StreamSource(new StringReader(xslStr));
TransformerFactory prettyPrint = TransformerFactory.newInstance()
Transformer transformer = prettyPrint.newTransformer(xslt);
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
transformer.setOutputProperty(OutputKeys.STANDALONE, "yes");
transformer.setOutputProperty(OutputKeys.METHOD, "xml");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new File(outputXML));
transformer.transform(source, result);
}
}
关于java - 需要对xml数据执行sql查询，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40720967/