druid加载MySQL驱动原理_【mysql】druid数据库连接池之sql解析原理
一、druid的sql解析包含四部分
词法分析器(Lexer)(单词分割，将sql语句中的关键词，标点，用户的相关信息提取出来)
语法分析器(Parser) (形式语言的语法解析，组装语法树)
抽象语法树(AST)(语法树)
语法树访问器(Visitor)对语法树进行遍历访问，采用访问者模式，将数据和行为进行分离的一种设计模式)
二、词法分析器(Lexer)
com.alibaba.druid.sql.parser.Lexer
com.alibaba.druid.sql.dialect.mysql.parser.Lexer
(1)词法分析的token内容
com.alibaba.druid.sql.parser.Token
com.alibaba.druid.sql.parser.Keywords
(2)词法分析的案例
/*** SELECT 关键字-select
* IDENTIFIER 标识符
* COMMA 关键字-标点符","
* IDENTIFIER
* COMMA
* IDENTIFIER
* FROM
* IDENTIFIER
* WHERE
* IDENTIFIER
* EQ 关键字-标点符"="
* QUES
* AND
* IDENTIFIER
* EQ
* LITERAL_INT
* ORDER
* BY
* IDENTIFIER
* DESC
* EOF 结束符号，标识sql终结*/
public static voidtest03() {
String sql= "select name,age,money from tb_order where id=? and status= 2 order by name desc";
Lexer lexer= newLexer(sql);for(; ; ) {
lexer.nextToken();
Token token=lexer.token();
System.out.println(token.name());if ("EOF".equals(token.name())) {break;
}
}
}
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三、语法分析器(Parser)
com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser
com.alibaba.druid.sql.parser.SQLStatementParser
com.alibaba.druid.sql.parser.SQLParser
四、抽象语法树(AST)
com.alibaba.druid.sql.ast.statement.SQLSelectStatement (select语句)
com.alibaba.druid.sql.ast.statement.SQLUpdateStatement (update语句)
com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlUpdateStatement (update语句)
com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlInsertStatement(insert语句)
com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlDeleteStatement(delete语句)
com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateServerStatement
com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateTableStatement
五、语法树访问器(Visitor)
com.alibaba.druid.sql.visitor.SQLASTVisitor
com.alibaba.druid.sql.visitor.SchemaStatVisitor
六、一个小案例
/*** sql语句的列名=>name
* sql语句的列名=>age
* sql语句的列名=>money
* sql语句的列名=>id
* sql语句的列名=>status
* 条件名=>tb_order.id
* 操作符=>=
* 值=>123
* 条件名=>tb_order.status
* 操作符=>=
* 值=>2
* 表名=>tb_order*/
public static voidtest02(){
String sql= "select name,age,money from tb_order where id=123 and status= 2 order by name desc";
List sqlStatements1=SQLUtils.parseStatements(sql,"mysql");
SQLStatement sqlStatement=sqlStatements1.get(0);
SchemaStatVisitor schemaStatVisitor=newSchemaStatVisitor();
sqlStatement.accept(schemaStatVisitor);//获取列信息
Collection columns=schemaStatVisitor.getColumns();for(TableStat.Column column:columns){
System.out.println("sql语句的列名=>"+column.getName());
}//获取条件信息
List conditions=schemaStatVisitor.getConditions();for(TableStat.Condition condition:conditions){
System.out.println("条件名=>"+condition.getColumn());
System.out.println("操作符=>"+condition.getOperator());
System.out.println("值=>"+condition.getValues().get(0));
}//获取表名
Map statMap=schemaStatVisitor.getTables();for(TableStat.Name name:statMap.keySet()){
System.out.println("表名=>"+name.getName());
}
}
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七、语法树节点分类
com.alibaba.druid.sql.ast.SQLObject
com.alibaba.druid.sql.ast.SQLStatement
com.alibaba.druid.sql.ast.SQLExpr
com.alibaba.druid.sql.ast.statement.SQLConstraint
详细描述：https://blog.csdn.net/qq_25104587/article/details/90577646