(1). 概述
前面对Liquibase进行了简单的集成,心里有一个疑问,Liquibase是如何把ChangLog(XML/JSON/YAML/SQLFile)进行解析,并执行的?
原理就在ChangeLogParser
(2). ChangeLogParser部析
从类图上就能看出来,ChangeLogParser支持:XML/JSON/YAML/SQLFile,我只对XML的实现感兴趣.
(3). AbstractChangeLogParser
public abstract class AbstractChangeLogParser implements ChangeLogParser {
@Override
public DatabaseChangeLog parse(String physicalChangeLogLocation, ChangeLogParameters changeLogParameters,
ResourceAccessor resourceAccessor) throws ChangeLogParseException {
// *************************************************************************************
// 1. 委托给子类:XMLChangeLogSAXParser对xml进行解析.
// *************************************************************************************
ParsedNode parsedNode = parseToNode(physicalChangeLogLocation, changeLogParameters, resourceAccessor);
if (parsedNode == null) {
return null;
}
// *************************************************************************************
// 2. 委托给:DatabaseChangeLog对xml解析后的内容,进行深度解析成业务模型
// *************************************************************************************
DatabaseChangeLog changeLog = new DatabaseChangeLog(physicalChangeLogLocation);
changeLog.setChangeLogParameters(changeLogParameters);
try {
//
changeLog.load(parsedNode, resourceAccessor);
} catch (Exception e) {
throw new ChangeLogParseException(e);
}
return changeLog;
}
protected abstract ParsedNode parseToNode(String physicalChangeLogLocation, ChangeLogParameters changeLogParameters,
ResourceAccessor resourceAccessor) throws ChangeLogParseException;
}
(4). XML解析入口:XMLChangeLogSAXParser
public class XMLChangeLogSAXParser extends AbstractChangeLogParser {
public static final String LIQUIBASE_SCHEMA_VERSION = "3.6";
private static final boolean PREFER_INTERNAL_XSD = Boolean.getBoolean("liquibase.prefer.internal.xsd");
private static final String XSD_FILE = "dbchangelog-" + LIQUIBASE_SCHEMA_VERSION + ".xsd";
private SAXParserFactory saxParserFactory;
public XMLChangeLogSAXParser() {
saxParserFactory = SAXParserFactory.newInstance();
saxParserFactory.setValidating(true);
saxParserFactory.setNamespaceAware(true);
if (PREFER_INTERNAL_XSD) {
InputStream xsdInputStream = XMLChangeLogSAXParser.class.getResourceAsStream(XSD_FILE);
if (xsdInputStream != null) {
try {
SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = schemaFactory.newSchema(new StreamSource(xsdInputStream));
saxParserFactory.setSchema(schema);
saxParserFactory.setValidating(false);
} catch (SAXException e) {
LogService.getLog(XMLChangeLogSAXParser.class).warning("Could not load " + XSD_FILE + ", enabling parser validator", e);
}
}
}
}
// *********************************************************************************************************
// 1. 对xml文件进行解析.
// *********************************************************************************************************
@Override
protected ParsedNode parseToNode(String physicalChangeLogLocation, ChangeLogParameters changeLogParameters,ResourceAccessor resourceAccessor) throws ChangeLogParseException {
try (
// 加载xml文佣
InputStream inputStream = StreamUtil.singleInputStream(physicalChangeLogLocation, resourceAccessor)) {
SAXParser parser = saxParserFactory.newSAXParser();
trySetSchemaLanguageProperty(parser);
XMLReader xmlReader = parser.getXMLReader();
LiquibaseEntityResolver resolver=new LiquibaseEntityResolver(this);
resolver.useResoureAccessor(resourceAccessor,FilenameUtils.getFullPath(physicalChangeLogLocation));
xmlReader.setEntityResolver(resolver);
xmlReader.setErrorHandler(new ErrorHandler() {
@Override
public void warning(SAXParseException exception) throws SAXException {
LogService.getLog(getClass()).warning(LogType.LOG, exception.getMessage());
throw exception;
}
@Override
public void error(SAXParseException exception) throws SAXException {
LogService.getLog(getClass()).severe(LogType.LOG, exception.getMessage());
throw exception;
}
@Override
public void fatalError(SAXParseException exception) throws SAXException {
LogService.getLog(getClass()).severe(LogType.LOG, exception.getMessage());
throw exception;
}
});
if (inputStream == null) {
if (physicalChangeLogLocation.startsWith("WEB-INF/classes/")) {
// Correct physicalChangeLogLocation and try again.
return parseToNode(
physicalChangeLogLocation.replaceFirst("WEB-INF/classes/", ""),
changeLogParameters, resourceAccessor);
} else {
throw new ChangeLogParseException(physicalChangeLogLocation + " does not exist");
}
}
XMLChangeLogSAXHandler contentHandler = new XMLChangeLogSAXHandler(physicalChangeLogLocation, resourceAccessor, changeLogParameters);
xmlReader.setContentHandler(contentHandler);
xmlReader.parse(new InputSource(new UtfBomStripperInputStream(inputStream)));
return contentHandler.getDatabaseChangeLogTree();
} catch (ChangeLogParseException e) {
throw e;
} catch (IOException e) {
throw new ChangeLogParseException("Error Reading Migration File: " + e.getMessage(), e);
} catch (SAXParseException e) {
throw new ChangeLogParseException("Error parsing line " + e.getLineNumber() + " column " + e.getColumnNumber() + " of " + physicalChangeLogLocation +": " + e.getMessage(), e);
} catch (SAXException e) {
Throwable parentCause = e.getException();
while (parentCause != null) {
if (parentCause instanceof ChangeLogParseException) {
throw ((ChangeLogParseException) parentCause);
}
parentCause = parentCause.getCause();
}
String reason = e.getMessage();
String causeReason = null;
if (e.getCause() != null) {
causeReason = e.getCause().getMessage();
}
if (reason == null) {
if (causeReason != null) {
reason = causeReason;
} else {
reason = "Unknown Reason";
}
}
throw new ChangeLogParseException("Invalid Migration File: " + reason, e);
} catch (Exception e) {
throw new ChangeLogParseException(e);
}
} // end parseToNode
}
(5). 解析XML转换成DatabaseChangeLog
public class DatabaseChangeLog implements Comparable<DatabaseChangeLog>, Conditional {
// *****************************************************************************
// 1. 解析xml内容,并转换到DatabaseChangeLog里
// *****************************************************************************
public void load(ParsedNode parsedNode, ResourceAccessor resourceAccessor)
throws ParsedNodeException, SetupException {
// 1.1 获得日志文件的详细路径
setLogicalFilePath(parsedNode.getChildValue(null, "logicalFilePath", String.class));
// 1.2 解析context
setContexts(new ContextExpression(parsedNode.getChildValue(null, "context", String.class)));
String objectQuotingStrategy = parsedNode.getChildValue(null, "objectQuotingStrategy", String.class);
if (objectQuotingStrategy != null) {
setObjectQuotingStrategy(ObjectQuotingStrategy.valueOf(objectQuotingStrategy));
}
// 1.3 遍历所有的xml子节点
for (ParsedNode childNode : parsedNode.getChildren()) {
handleChildNode(childNode, resourceAccessor);
}
} //end load
protected void handleChildNode(ParsedNode node, ResourceAccessor resourceAccessor)
throws ParsedNodeException, SetupException {
expandExpressions(node);
String nodeName = node.getName();
switch (nodeName) {
// *************************************************************************************************
// 1.4 对<changeSet>进行解析
// *************************************************************************************************
case"changeSet":
// 如果dbms match
if (isDbmsMatch(node.getChildValue(null, "dbms", String.class))) {
//
this.addChangeSet(createChangeSet(node, resourceAccessor));
}
break;
// *************************************************************************************************
// 1.5 对<include>进行解析
// *************************************************************************************************
case"include": {
String path = node.getChildValue(null, "file", String.class);
if (path == null) {
throw new UnexpectedLiquibaseException("No 'file' attribute on 'include'");
}
path = path.replace('\\', '/');
ContextExpression includeContexts = new ContextExpression(node.getChildValue(null, "context", String.class));
try {
include(path, node.getChildValue(null, "relativeToChangelogFile", false), resourceAccessor, includeContexts, true);
} catch (LiquibaseException e) {
throw new SetupException(e);}
break;
}
// *************************************************************************************************
// 1.6 对<includeAll>进行解析
// *************************************************************************************************
case "includeAll": {
String path = node.getChildValue(null, "path", String.class);
String resourceFilterDef = node.getChildValue(null, "filter", String.class);
if (resourceFilterDef == null) {
resourceFilterDef = node.getChildValue(null, "resourceFilter", String.class);
}
IncludeAllFilter resourceFilter = null;
if (resourceFilterDef != null) {
try {
resourceFilter = (IncludeAllFilter) Class.forName(resourceFilterDef).getConstructor().newInstance();
} catch (ReflectiveOperationException e) {
throw new SetupException(e);
}
}
String resourceComparatorDef = node.getChildValue(null, "resourceComparator", String.class);
Comparator<String> resourceComparator = null;
if (resourceComparatorDef != null) {
try {
resourceComparator = (Comparator<String>) Class.forName(resourceComparatorDef).getConstructor().newInstance();
} catch (ReflectiveOperationException e) {
//take default comparator
LogService.getLog(getClass()).info(LogType.LOG, "no resourceComparator defined - taking default " +
"implementation");
resourceComparator = getStandardChangeLogComparator();
}
}
ContextExpression includeContexts = new ContextExpression(node.getChildValue(null, "context", String.class));
includeAll(path, node.getChildValue(null, "relativeToChangelogFile", false), resourceFilter,
node.getChildValue(null, "errorIfMissingOrEmpty", true),
resourceComparator, resourceAccessor, includeContexts);
break;
}
// *************************************************************************************************
// 1.7 对<preConditions>进行解析
// *************************************************************************************************
case "preConditions": {
this.preconditionContainer = new PreconditionContainer();
try {
this.preconditionContainer.load(node, resourceAccessor);
} catch (ParsedNodeException e) {
e.printStackTrace();
}
break;
}
// *************************************************************************************************
// 1.8 对<property>进行解析
// *************************************************************************************************
case "property": {
try {
String context = node.getChildValue(null, "context", String.class);
String dbms = node.getChildValue(null, "dbms", String.class);
String labels = node.getChildValue(null, "labels", String.class);
Boolean global = node.getChildValue(null, "global", Boolean.class);
if (global == null) {
// okay behave like liquibase < 3.4 and set global == true
global = true;
}
String file = node.getChildValue(null, "file", String.class);
if (file == null) {
// direct referenced property, no file
String name = node.getChildValue(null, "name", String.class);
String value = node.getChildValue(null, "value", String.class);
this.changeLogParameters.set(name, value, context, labels, dbms, global, this);
} else {
// read properties from the file
Properties props = new Properties();
InputStream propertiesStream = StreamUtil.singleInputStream(file, resourceAccessor);
if (propertiesStream == null) {
LogService.getLog(getClass()).info(LogType.LOG, "Could not open properties file " + file);
} else {
props.load(propertiesStream);
for (Map.Entry entry : props.entrySet()) {
this.changeLogParameters.set(
entry.getKey().toString(),
entry.getValue().toString(),
context,
labels,
dbms,
global,
this
);
}
}
}
} catch (IOException e) {
throw new ParsedNodeException(e);
}
break;
}
}
} // end handleChildNode
// ****************************************************************
// 1.4.1 对<changeSet>进行解析,并转换成:ChangeSet对象
// ****************************************************************
protected ChangeSet createChangeSet(ParsedNode node, ResourceAccessor resourceAccessor) throws ParsedNodeException {
ChangeSet changeSet = new ChangeSet(this);
changeSet.setChangeLogParameters(this.getChangeLogParameters());
changeSet.load(node, resourceAccessor);
return changeSet;
}
}
(6). ChangeSet对象
public class ChangeSet implements Conditional, ChangeLogChild {
// ********************************************************************************
// 1. 创建ChangeSet,解析xml,并把xml内容转换到:ChangeSet对象里.
// ********************************************************************************
public void load(ParsedNode node, ResourceAccessor resourceAccessor) throws ParsedNodeException {
// <changeSet id="1">
this.id = node.getChildValue(null, "id", String.class);
// <changeSet author="nvoxland">
this.author = node.getChildValue(null, "author", String.class);
// runAlways
this.alwaysRun = node.getChildValue(null, "runAlways", node.getChildValue(null, "alwaysRun", false));
// runOnChange
this.runOnChange = node.getChildValue(null, "runOnChange", false);
// context
this.contexts = new ContextExpression(node.getChildValue(null, "context", String.class));
//
this.labels = new Labels(StringUtils.trimToNull(node.getChildValue(null, "labels", String.class)));
// <changeSet id="1" author="nvoxland" dbms="" >
setDbms(node.getChildValue(null, "dbms", String.class));
//
this.runInTransaction = node.getChildValue(null, "runInTransaction", true);
this.created = node.getChildValue(null, "created", String.class);
this.runOrder = node.getChildValue(null, "runOrder", String.class);
this.ignore = node.getChildValue(null, "ignore", false);
this.comments = StringUtils.join(node.getChildren(null, "comment"), "\n", new StringUtils.StringUtilsFormatter() {
@Override
public String toString(Object obj) {
if (((ParsedNode) obj).getValue() == null) {
return "";
} else {
return ((ParsedNode) obj).getValue().toString();
}
}
});
this.comments = StringUtils.trimToNull(this.comments);
String objectQuotingStrategyString = StringUtils.trimToNull(node.getChildValue(null, "objectQuotingStrategy", String.class));
if (changeLog != null) {
this.objectQuotingStrategy = changeLog.getObjectQuotingStrategy();
}
if (objectQuotingStrategyString != null) {
this.objectQuotingStrategy = ObjectQuotingStrategy.valueOf(objectQuotingStrategyString);
}
if (this.objectQuotingStrategy == null) {
this.objectQuotingStrategy = ObjectQuotingStrategy.LEGACY;
}
// xml文件位置
this.filePath = StringUtils.trimToNull(node.getChildValue(null, "logicalFilePath", String.class));
if (filePath == null) {
filePath = changeLog.getFilePath();
}
this.setFailOnError(node.getChildValue(null, "failOnError", Boolean.class));
String onValidationFailString = node.getChildValue(null, "onValidationFail", "HALT");
this.setOnValidationFail(ValidationFailOption.valueOf(onValidationFailString));
for (ParsedNode child : node.getChildren()) { // 循环解析余下的所有子节点
// ********************************************************************************
// 2. 解析<changeSet> ... </changeSet>下所有的内容.
// ********************************************************************************
handleChildNode(child, resourceAccessor);
}
} // end load
// ********************************************************************************
// 3. 解析<changeSet>下所有内容.
// ********************************************************************************
protected void handleChildNode(ParsedNode child, ResourceAccessor resourceAccessor) throws ParsedNodeException {
switch (child.getName()) {
case "rollback": // 解析rollback
handleRollbackNode(child, resourceAccessor);
break;
case "validCheckSum":
case "validCheckSums": // 解析validCheckSums
if (child.getValue() == null) {
return;
}
if (child.getValue() instanceof Collection) {
for (Object checksum : (Collection) child.getValue()) {
addValidCheckSum((String) checksum);
}
} else {
addValidCheckSum(child.getValue(String.class));
}
break;
case "modifySql": // 解析modifySql
String dbmsString = StringUtils.trimToNull(child.getChildValue(null, "dbms", String.class));
String contextString = StringUtils.trimToNull(child.getChildValue(null, "context", String.class));
String labelsString = StringUtils.trimToNull(child.getChildValue(null, "labels", String.class));
boolean applyToRollback = child.getChildValue(null, "applyToRollback", false);
Set<String> dbms = new HashSet<>();
if (dbmsString != null) {
dbms.addAll(StringUtils.splitAndTrim(dbmsString, ","));
}
ContextExpression context = null;
if (contextString != null) {
context = new ContextExpression(contextString);
}
Labels labels = null;
if (labelsString != null) {
labels = new Labels(labelsString);
}
List<ParsedNode> potentialVisitors = child.getChildren();
for (ParsedNode node : potentialVisitors) {
SqlVisitor sqlVisitor = SqlVisitorFactory.getInstance().create(node.getName());
if (sqlVisitor != null) {
sqlVisitor.setApplyToRollback(applyToRollback);
if (!dbms.isEmpty()) {
sqlVisitor.setApplicableDbms(dbms);
}
sqlVisitor.setContexts(context);
sqlVisitor.setLabels(labels);
sqlVisitor.load(node, resourceAccessor);
addSqlVisitor(sqlVisitor);
}
}
break;
case "preConditions": // 解析preConditions
this.preconditions = new PreconditionContainer();
try {
this.preconditions.load(child, resourceAccessor);
} catch (ParsedNodeException e) {
e.printStackTrace();
}
break;
case "changes": // 解析changes
for (ParsedNode changeNode : child.getChildren()) {
handleChildNode(changeNode, resourceAccessor);
}
break;
default:
// *********************************************************************************
// 4. 解析其它(createTable/addColumn/insert/...)标签.
// *********************************************************************************
Change change = toChange(child, resourceAccessor);
if ((change == null) && (child.getValue() instanceof String)) {
this.setAttribute(child.getName(), child.getValue());
} else {
addChange(change);
}
break;
}
}// end handleChildNode
// ************************************************************************
// 5. 解析其它(createTable/addColumn/insert/...)标签,通过Change进行承载
// ************************************************************************
protected Change toChange(ParsedNode value, ResourceAccessor resourceAccessor) throws ParsedNodeException {
// **********************************************************************
// 通过SPI,加载(liquibase.change.Change)的所有实现类,这样就能实现动态解析XML的标签了
// **********************************************************************
Change change = ChangeFactory.getInstance().create(value.getName());
if (change == null) {
return null;
} else {
// **********************************************************************
// 调用Change.load方法,解析所有的标签,在这里以:InsertDataChange为案例
// **********************************************************************
change.load(value, resourceAccessor);
return change;
}
} // end toChange
}
(7). InsertDataChange
<!-- 对insert标签进行解析 -->
<changeSet id="5" author="nvoxland" context="test">
<insert tableName="person">
<column name="firstname" value="John"/>
<column name="lastname" value="Doe"/>
<column name="username" value="jdoe"/>
</insert>
</changeSet>
package liquibase.change.core;
@DatabaseChange(name="insert", description = "Inserts data into an existing table", priority = ChangeMetaData.PRIORITY_DEFAULT, appliesTo = "table")
public class InsertDataChange extends AbstractChange implements ChangeWithColumns<ColumnConfig>, DbmsTargetedChange {
private String catalogName;
private String schemaName;
private String tableName;
private List<ColumnConfig> columns;
private String dbms;
// ...
}
(9). 总结
通过对源码的剖析,我们能知道Liquibase的业务模型(如下图),后面,会继续对Liquibase是如何执行SQL进行剖析.
