使⽤JavaStAX解析超⼤xml（超过60g）⽂件，并将其存⼊数
据库（MySQL）
遇到的问题
本⼈需要解析Stack Overflow的（xml格式）将数据其存⼊数据库，其中关于Stack Overflow帖⼦（Posts）的xml⽂件超过了60G。
那么如何解析那么⼤的xml⽂件呢（Stack Overflow上有解决⽅案-）？
解决⽅案
或许你已经想到了分块读取，然后解析。那么如何分块解析呢？Java中处理xml⽂件有两种处理⽅案（DOM和Event Driven）。DOM需要
将所有⽂件读取，在内存中构建DOM树，显然这种⽅案不⾏；只能选择基于事件的⽅式，本⼈选择了StAX，或许⽤SAX的⼈⽐较多，那么
SAX和StAX的区别是什么呢？，这是说明： 。
java xml是什么
你需要了解的是：什么是事件驱动。（懂得这个，也就懂得了StAX为什么是分块处理了）
代码实现
<?xml version="1.0" encoding="utf-8"?>
<posts>
<row Id="4" PostTypeId="1" AcceptedAnswerId="7" CreationDate="2008-07-31T21:42:52.667" Score="573" ViewCount="37080" Body="" OwnerUserId="8" LastE <row Id="6" PostTypeId="1" AcceptedAnswerId="31" CreationDate="2008-07-31T22:08:08.620" Score="256" ViewCount="16306" Body="" OwnerUserId="9" Las <row Id="7" PostTypeId="2" ParentId="4" CreationDate="2008-07-31T22:17:57.883" Score="401" Body="" OwnerUserId="9" LastEditorUserId="4020527" LastEd <row Id="9" PostTypeId="1" AcceptedAnswerId="1404" CreationDate="2008-07-31T23:40:59.743" Score="1743" ViewCount="480476" Body="" OwnerUserId="1 <row Id="11" PostTypeId="1" AcceptedAnswerId="1248" CreationDate="2008-07-31T23:55:37.967" Score="1348" ViewCount="136033" Body="" OwnerUserId=" <row Id="12" PostTy
peId="2" ParentId="11" CreationDate="2008-07-31T23:56:41.303" Score="320" Body="" OwnerUserId="1" LastEditorUserId="1271898" Las <row Id="13" PostTypeId="1" CreationDate="2008-08-01T00:42:38.903" Score="539" ViewCount="157009" Body="" OwnerUserId="9" LastEditorUserId="532136 </posts>
数据库设计
由于帖⼦（Post）可以分为两种问题和回答（通过属性PostTypeId的值确定），因为数据量很⼤（4200万⾏左右），所以我设计了两张
表。
-- PostTypeId = 1
-- Id CreationDate Score ViewCount OwnerUserId Tags AnswerCount FavoriteCount CREATE TABLE `questions` (
`Id` int,
`CreationDate` datetime,
`Score` int,
`ViewCount` int,
`OwnerUserId` int,
`Tags` varchar(250),
`AnswerCount` int,
`FavoriteCount` int,
PRIMARY KEY (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
-- PostTypeId = 2
--Id ParentId CreationDate Score CommentCount
CREATE TABLE `answers` (
`Id` int,
`ParentId` int,
`CreationDate` datetime,
`Score` int,
`OwnerUserId` int,
`CommentCount` int,
PRIMARY KEY (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
Java代码
sql.jdbc.PreparedStatement;
l.XMLConstants;
l.stream.XMLInputFactory;
l.stream.XMLStreamException;
l.stream.XMLStreamReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Date;
/
**
* Desc: Parse & Import(to mysql db) Stack Overflow dump xml file
* Created by Myth on 10/12/2018
*/
public class XmlProcessor {
private Connection connection = null;
/**
* Get Db Connection
* @throws ClassNotFoundException
* @throws SQLException
*/
public void openMysqlConnection() throws ClassNotFoundException, SQLException { String driver = "sql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/stackoverflow";
String username = "root";
String password = "123456";
Connection connection = null;
Class.forName(driver);
connection = Connection(url, username, password);
}
public void closeConnection() throws SQLException {
}
/**
*
* @param filePath
* @param 每 commitCount ⾏提交⼀次
* @throws SQLException
* @throws FileNotFoundException
* @throws XMLStreamException
*/
public void parsePosts(String filePath, int commitCount) throws SQLException, FileNotFoundException, XMLStreamException { // 计时器 starts
Long begin = new Date().getTime();
// 组合sql语句
String prefixQuestions = "INSERT INTO questions VALUES ";
String prefixAnswers = "INSERT INTO answers VALUES ";
StringBuffer suffixQuestions = new StringBuffer();
StringBuffer suffixAnswers = new StringBuffer();
// 设置事务为⾮⾃动提交
// PreparedStatement 执⾏ sql语句
PreparedStatement pst = (PreparedStatement) tion.prepareStatement("");
// 解析xml获得数据
XMLInputFactory inputFactory = wInstance();
inputFactory.setProperty("acle/xml/jaxp/properties/getEntityCountInfo", "yes");
// 设置entity size , 否则会报 JAXP00010004 错误
inputFactory.setProperty("acle/xml/jaxp/properties/totalEntitySizeLimit", Integer.MAX_VALUE);
File file = new File(filePath);
InputStream isS= new FileInputStream(file);
XMLStreamReader streamReader = ateXMLStreamReader(isS);
int countRow = 0;
// Q: Id CreationDate Score ViewCount OwnerUserId Tags AnswerCount FavoriteCount
// A: Id ParentId CreationDate Score CommentCount
String id, creationDate, score, viewCount, ownerUserId, tags, answerCount, favoriteCount, parentId, commentCount;
String postTypeId;
String sqlQuestions = null, sqlAnswers = null;
// 存储数据
while(streamReader.hasNext()) {
<();
EventType() == XMLStreamReader.START_ELEMENT){
if (LocalName().equals("row")) {
postTypeId = AttributeValue(null,"PostTypeId");
id = AttributeValue(null,"Id");
creationDate = AttributeValue(null,"CreationDate");
score = AttributeValue(null,"Score");
viewCount = AttributeValue(null,"ViewCount");
ownerUserId = AttributeValue(null,"OwnerUserId");
tags = AttributeValue(null,"Tags");
answerCount = AttributeValue(null,"AnswerCount");
favoriteCount = AttributeValue(null,"FavoriteCount");
parentId = AttributeValue(null,"ParentId");
commentCount = AttributeValue(null,"CommentCount");
// 1 Question, 2 Answer
if ("1".equals(postTypeId)) {
suffixQuestions.append("(" + id + "," + "\"" + creationDate + "\"" + "," +
score + "," + viewCount + "," + ownerUserId + "," +
"\"" + tags + "\"" + "," + answerCount + "," + favoriteCount + "),");
} else {
suffixAnswers.append("(" + id + "," + parentId + "," + "\"" + creationDate + "\"" + "," +
score + "," + ownerUserId + "," + commentCount + "),");
}
countRow += 1; // 记录⾏数
if (countRow % commitCount == 0) {
// System.out.print("Count: " + String(count));
// 构建完整sql
sqlQuestions = prefixQuestions + suffixQuestions.substring(0, suffixQuestions.length() - 1); sqlAnswers = prefixAnswers + suffixAnswers.substring(0, suffixAnswers.length() - 1);
// 添加执⾏sql
pst.addBatch(sqlQuestions);
pst.addBatch(sqlAnswers);
// 执⾏操作
// 提交事务
// 清空上⼀次添加的数据
suffixQuestions = new StringBuffer();
suffixAnswers = new StringBuffer();
System.out.println("Committed: " + countRow + " √");
}
}
}
}
if (suffixQuestions.length() != 0) {
sqlQuestions = prefixQuestions + suffixQuestions.substring(0, suffixQuestions.length() - 1);
pst.addBatch(sqlQuestions);
connectionmit();
}
if (suffixAnswers.length() != 0) {
sqlAnswers = prefixAnswers + suffixAnswers.substring(0, suffixAnswers.length() - 1);
/
/ System.out.println(suffixAnswers.substring(0, suffixAnswers.length() - 1));
pst.addBatch(sqlAnswers);
connectionmit();
}
System.out.println("Committed All: " + countRow + " √");
pst.close();
// 耗时
Long end = new Date().getTime();
System.out.println("Cast : " + (end - begin) / 1000 + " s");
}
}
⼤约需要10多分钟就可以将全部数据（4200多万⾏）导⼊。
总结
Bug
Exception in thread "main" l.stream.XMLStreamException: ParseError at [row,col]:[1077158,4084]
Message: JAXP00010004: The accumulated size of entities is "50,000,001" that exceeded the "50,000,000" limit set by "FEATURE_SECURE_PROCESSING".
原因：java xml解析器⾃带limit（），⽤来控制读⼊的⼤⼩、控制内存..... 因为要处理的xml⽂件过⼤，超过了默认的limit，所以在java代码71⾏，设置了limit的⼤⼩，但是即使设置最⼤，也勉强能够处理4000多万条数据，如果超过这个数量，就不能通过这个⽅法了，可以将超⼤的xml切分成⼏个xml⽂件，然后按照上述处理。
其他问题
使⽤batch 插⼊，可以提⾼效率
使⽤ XMLStreamReader ⽽不⽤ XMLEventReader（区别见官⽅⽂档、教程）提⾼效率
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