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這篇文章主要介紹“sharding-jdbc的ANTLR4 SQL用法實例”，在日常操作中，相信很多人在sharding-jdbc的ANTLR4 SQL用法實例問題上存在疑惑，小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”sharding-jdbc的ANTLR4 SQL用法實例”的疑惑有所幫助！接下來，請跟著小編一起來學習吧！
Sharding主要利用ANTLR4來解析SQL，以mysql為例，分析源碼前可以先了解以下三點：
antlr4，如何編寫 .g4 語法文件
mysql 語法可以參考https://dev.mysql.com/doc/refman/8.0/en/sql-syntax-data-manipulation.html
mysql g4文件編寫可以參考https://github.com/antlr/grammars-v4/blob/master/mysql
1.解析入口ParsingSQLRouter#parse
/**
* 解析sql
*
* @param logicSQL 邏輯sql
* @param useCache 是否緩存解析后的結果
* @return
*/
@Override
public SQLStatement parse(final String logicSQL, final boolean useCache) {
//解析前鉤子，如:調用鏈etx
parsingHook.start(logicSQL);
try {
//解析SQL
SQLStatement result = new ShardingSQLParseEntry(databaseType, shardingMetaData.getTable(), parsingResultCache).parse(logicSQL, useCache);
//解析成功后鉤子
parsingHook.finishSuccess(result, shardingMetaData.getTable());
return result;
// CHECKSTYLE:OFF
} catch (final Exception ex) {
// CHECKSTYLE:ON
//解析失敗鉤子
parsingHook.finishFailure(ex);
throw ex;
}
}public final class ShardingSQLParseEntry extends SQLParseEntry {
private final DatabaseType databaseType;
private final ShardingTableMetaData shardingTableMetaData;
public ShardingSQLParseEntry(final DatabaseType databaseType, final ShardingTableMetaData shardingTableMetaData, final ParsingResultCache parsingResultCache) {
super(parsingResultCache);
this.databaseType = databaseType;
this.shardingTableMetaData = shardingTableMetaData;
}
/**
* 根據sql獲取解析引擎封裝對象
*/
@Override
protected SQLParseEngine getSQLParseEngine(final String sql) {
//參數1：單例，加載statement、提取、過濾配置文件
//參數2：數據庫類型
//參數3：需要解析sql
//參數4：分片表元數據
return new SQLParseEngine(ShardingParseRuleRegistry.getInstance(), databaseType, sql, shardingTableMetaData);
}
}2.ShardingParseRuleRegistry.getInstance()->ParseRuleRegistry#initParseRuleDefinition加載statement、提取、過濾配置文件
private void initParseRuleDefinition() {
//利用JAXB加載META-INF/parsing-rule-definition/extractor-rule-definition.xml配置文件
ExtractorRuleDefinitionEntity generalExtractorRuleEntity = extractorRuleLoader.load(RuleDefinitionFileConstant.getExtractorRuleDefinitionFile());
//利用JAXB加載下META-INF/parsing-rule-definition/filler-rule-definition.xml配置文件
FillerRuleDefinitionEntity generalFillerRuleEntity = fillerRuleLoader.load(RuleDefinitionFileConstant.getFillerRuleDefinitionFile());
//加對應類型(sharding、masterslave、encrypt)配置文件
//META-INF/parsing-rule-definition/sharding/filler-rule-definition.xml
FillerRuleDefinitionEntity featureGeneralFillerRuleEntity = fillerRuleLoader.load(RuleDefinitionFileConstant.getFillerRuleDefinitionFile(getType()));
//根據數據庫類型加載對應的配置文件
for (DatabaseType each : SQLParserFactory.getAddOnDatabaseTypes()) {
//META-INF/parsing-rule-definition/sharding.mysql/filler-rule-definition.xml
//databaseType:rules<segment,filler>
fillerRuleDefinitions.put(each, createFillerRuleDefinition(generalFillerRuleEntity, featureGeneralFillerRuleEntity, each));
//META-INF/parsing-rule-definition/sharding.mysql/extractor-rule-definition.xml
//META-INF/parsing-rule-definition/sharding.mysql/sql-statement-rule-definition.xml
//databaseType:rules<xxxContext,SQLStatementRule>
sqlStatementRuleDefinitions.put(each, createSQLStatementRuleDefinition(generalExtractorRuleEntity, each));
}
}
private FillerRuleDefinition createFillerRuleDefinition(final FillerRuleDefinitionEntity generalFillerRuleEntity,
final FillerRuleDefinitionEntity featureGeneralFillerRuleEntity, final DatabaseType databaseType) {
return new FillerRuleDefinition(
generalFillerRuleEntity, featureGeneralFillerRuleEntity, fillerRuleLoader.load(RuleDefinitionFileConstant.getFillerRuleDefinitionFile(getType(), databaseType)));
}
private SQLStatementRuleDefinition createSQLStatementRuleDefinition(final ExtractorRuleDefinitionEntity generalExtractorRuleEntity, final DatabaseType databaseType) {
//將所有提取器封裝到一起
//id:extractor
ExtractorRuleDefinition extractorRuleDefinition = new ExtractorRuleDefinition(
generalExtractorRuleEntity, extractorRuleLoader.load(RuleDefinitionFileConstant.getExtractorRuleDefinitionFile(getType(), databaseType)));
//sql-statement-rule-definition.xml
//Context:SQLStatementRule
//SQLStatementRule封裝statement對應的提取器
return new SQLStatementRuleDefinition(statementRuleLoader.load(RuleDefinitionFileConstant.getSQLStatementRuleDefinitionFile(getType(), databaseType)), extractorRuleDefinition);
}3.SQLParseEntry#parse，這里抽象SQLParseEntry，主要有不同入口（EncryptSQLParseEntry、MasterSlaveSQLParseEntry、ShardingSQLParseEntry）
@RequiredArgsConstructor
public abstract class SQLParseEntry {
private final ParsingResultCache parsingResultCache;
/**
* Parse SQL.
*
* @param sql SQL
* @param useCache use cache or not
* @return SQL statement
*/
public final SQLStatement parse(final String sql, final boolean useCache) {
//從緩存中獲取解析后的SQLStatement
Optional<SQLStatement> cachedSQLStatement = getSQLStatementFromCache(sql, useCache);
if (cachedSQLStatement.isPresent()) {
return cachedSQLStatement.get();
}
//解析
SQLStatement result = getSQLParseEngine(sql).parse();
//cache
if (useCache) {
parsingResultCache.put(sql, result);
}
return result;
}
private Optional<SQLStatement> getSQLStatementFromCache(final String sql, final boolean useCache) {
return useCache ? Optional.fromNullable(parsingResultCache.getSQLStatement(sql)) : Optional.<SQLStatement>absent();
}
//根據子類ShardingSQLParseEntry的getSQLParseEngine獲取SQLParseEngine
protected abstract SQLParseEngine getSQLParseEngine(String sql);
}4.SQLParseEngine#parse，包含解析、提取、填充SQLStatement
public SQLParseEngine(final ParseRuleRegistry parseRuleRegistry, final DatabaseType databaseType, final String sql, final ShardingTableMetaData shardingTableMetaData) {
DatabaseType trunkDatabaseType = DatabaseTypes.getTrunkDatabaseType(databaseType.getName());
//sql解析引擎
parserEngine = new SQLParserEngine(parseRuleRegistry, trunkDatabaseType, sql);
//sql提取引擎
extractorEngine = new SQLSegmentsExtractorEngine();
//sql填充引擎
fillerEngine = new SQLStatementFillerEngine(parseRuleRegistry, trunkDatabaseType, sql, shardingTableMetaData);
}
/**
* Parse SQL.
*
* @return SQL statement
*/
public SQLStatement parse() {
//利用ANTLR4 解析sql
SQLAST ast = parserEngine.parse();
//提取ast中的token，封裝成對應的segment，如TableSegment、IndexSegment
Collection<SQLSegment> sqlSegments = extractorEngine.extract(ast);
Map<ParserRuleContext, Integer> parameterMarkerIndexes = ast.getParameterMarkerIndexes();
//填充SQLStatement
return fillerEngine.fill(sqlSegments, parameterMarkerIndexes.size(), ast.getSqlStatementRule());
}5.SQLParserEngine#parse，解析SQL，封裝AST(Abstract Syntax Tree 抽象語法樹)
public SQLAST parse() {
//SPI 利用ANTLR4解析獲取SQLParser(MySQLParserEntry)執行，獲取解析樹
ParseTree parseTree = SQLParserFactory.newInstance(databaseType, sql).execute().getChild(0);
if (parseTree instanceof ErrorNode) {
throw new SQLParsingException(String.format("Unsupported SQL of `%s`", sql));
}
//獲取配置文件中的StatementContext，比如CreateTableContext、SelectContext
SQLStatementRule sqlStatementRule = parseRuleRegistry.getSQLStatementRule(databaseType, parseTree.getClass().getSimpleName());
if (null == sqlStatementRule) {
throw new SQLParsingException(String.format("Unsupported SQL of `%s`", sql));
}
//封裝ast(Abstract Syntax Tree 抽象語法樹)
return new SQLAST((ParserRuleContext) parseTree, getParameterMarkerIndexes((ParserRuleContext) parseTree), sqlStatementRule);
}
/**
* 遞歸獲取所有參數占位符
*
* @param rootNode 根節點
* @return
*/
private Map<ParserRuleContext, Integer> getParameterMarkerIndexes(final ParserRuleContext rootNode) {
Collection<ParserRuleContext> placeholderNodes = ExtractorUtils.getAllDescendantNodes(rootNode, RuleName.PARAMETER_MARKER);
Map<ParserRuleContext, Integer> result = new HashMap<>(placeholderNodes.size(), 1);
int index = 0;
for (ParserRuleContext each : placeholderNodes) {
result.put(each, index++);
}
return result;
}6.使用SQLParserFactory#newInstance創建SQLParser
/**
* New instance of SQL parser.
*
* @param databaseType database type
* @param sql SQL
* @return SQL parser
*/
public static SQLParser newInstance(final DatabaseType databaseType, final String sql) {
//SPI load所有擴展
for (SQLParserEntry each : NewInstanceServiceLoader.newServiceInstances(SQLParserEntry.class)) {
//判斷數據庫類型
if (DatabaseTypes.getActualDatabaseType(each.getDatabaseType()) == databaseType) {
//解析sql
return createSQLParser(sql, each);
}
}
throw new UnsupportedOperationException(String.format("Cannot support database type '%s'", databaseType));
}
@SneakyThrows
private static SQLParser createSQLParser(final String sql, final SQLParserEntry parserEntry) {
//詞法分析器
Lexer lexer = parserEntry.getLexerClass().getConstructor(CharStream.class).newInstance(CharStreams.fromString(sql));
//語法分析器
return parserEntry.getParserClass().getConstructor(TokenStream.class).newInstance(new CommonTokenStream(lexer));
}7.以select為例，分析第四步的SQL解析、提取、填充過程
利用idea的antlr4插件，使用Sharding的mysql .g4 文件解析SQL；如圖：
參考上圖，使用sharding parse解析模塊提取(extractor) ParserRuleContext對應的參數封裝成Segment
8.SQLSegmentsExtractorEngine#extract，參考第七部圖，根據SQLStatementRule->tableReferences, columns, selectItems, where, predicate, groupBy, orderBy, limit, subqueryPredicate對應的提取器，生成對應類型的Segment
public final class SQLSegmentsExtractorEngine {
/**
* Extract SQL segments.
*
* @param ast SQL AST
* @return SQL segments
*/
public Collection<SQLSegment> extract(final SQLAST ast) {
Collection<SQLSegment> result = new LinkedList<>();
//遍歷Context對應提取器，封裝成對應對應類型的Segment，比如TableSegment、IndexSegment
//以SELECT i.* FROM t_order o, t_order_item i WHERE o.order_id = i.order_id and o.order_id = ?為例
//SelectContext->SQLStatementRule
//SQLStatementRule->tableReferences, columns, selectItems, where, predicate, groupBy, orderBy, limit, subqueryPredicate
//分析九個提取器
for (SQLSegmentExtractor each : ast.getSqlStatementRule().getExtractors()) {
//分兩種類型
//1.單一樹，直接提取單一RuleName下的token；參看sql解析后的語法樹對比比較清晰
if (each instanceof OptionalSQLSegmentExtractor) {
Optional<? extends SQLSegment> sqlSegment = ((OptionalSQLSegmentExtractor) each).extract(ast.getParserRuleContext(), ast.getParameterMarkerIndexes());
if (sqlSegment.isPresent()) {
result.add(sqlSegment.get());
}
//2.分叉樹，需遍歷提取RuleName下的所有Token；參看sql解析后的語法樹對比比較清晰
} else if (each instanceof CollectionSQLSegmentExtractor) {
result.addAll(((CollectionSQLSegmentExtractor) each).extract(ast.getParserRuleContext(), ast.getParameterMarkerIndexes()));
}
}
return result;
}
}9.SQLStatementFillerEngine#fill，封裝SQLStatement，填充Segment
@RequiredArgsConstructor
public final class SQLStatementFillerEngine {
private final ParseRuleRegistry parseRuleRegistry;
private final DatabaseType databaseType;
private final String sql;
private final ShardingTableMetaData shardingTableMetaData;
/**
* Fill SQL statement.
*
* @param sqlSegments SQL segments
* @param parameterMarkerCount parameter marker count
* @param rule SQL statement rule
* @return SQL statement
*/
@SneakyThrows
public SQLStatement fill(final Collection<SQLSegment> sqlSegments, final int parameterMarkerCount, final SQLStatementRule rule) {
//如SelectStatement
SQLStatement result = rule.getSqlStatementClass().newInstance();
//邏輯sql
result.setLogicSQL(sql);
//參數個數
result.setParametersCount(parameterMarkerCount);
//segment
result.getSQLSegments().addAll(sqlSegments);
//遍歷填充對應類型的Segment
for (SQLSegment each : sqlSegments) {
//根據數據庫類型、segment找到對應填充器，來填充對應的segment
//如：TableSegment->TableFiller
Optional<SQLSegmentFiller> filler = parseRuleRegistry.findSQLSegmentFiller(databaseType, each.getClass());
if (filler.isPresent()) {
doFill(each, result, filler.get());
}
}
return result;
}
@SuppressWarnings("unchecked")
private void doFill(final SQLSegment sqlSegment, final SQLStatement sqlStatement, final SQLSegmentFiller filler) {
//添加字段、字段約束、修改字段、字段命令，這四種填充器需要設置分片表元數據
//主要通過分片表元數據來填充對應的SQLStatement
if (filler instanceof ShardingTableMetaDataAware) {
((ShardingTableMetaDataAware) filler).setShardingTableMetaData(shardingTableMetaData);
}
//如:
//利用TableFill來填充SelectStatement#tables
filler.fill(sqlSegment, sqlStatement);
}
}以上Sharding的SQL解析大概過程，解析ParserRuleContext提取封裝對應的Segment，最后封裝SQLStatement，并根據Segment對應的Filler來填充SQLStatement；具體如何提取、填充可以查看以下三個文件
extractor-rule-definition.xml
filler-rule-definition.xml
sql-statement-rule-definition.xml
到此，關于“sharding-jdbc的ANTLR4 SQL用法實例”的學習就結束了，希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學習，快去試試吧！若想繼續學習更多相關知識，請繼續關注億速云網站，小編會繼續努力為大家帶來更多實用的文章！
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