要实现一个Java SQL解析器,可以按照以下步骤进行:
1、定义词法分析器(Lexer)
2、定义语法分析器(Parser)
3、定义SQL语句的抽象语法树(AST)
4、遍历AST并执行相应的操作
下面是详细的实现过程:
1. 定义词法分析器(Lexer)
需要定义一个词法分析器,用于将输入的SQL语句分割成一个个的词法单元,可以使用正则表达式来匹配不同的词法单元。
import java.util.ArrayList; import java.util.List; import java.util.regex.Matcher; import java.util.regex.Pattern; public class SqlLexer { private static final String SQL_COMMENT = "[^ ]*"; private static final String SQL_STRING = "'[^']*'|("[^"]*")"; private static final String SQL_WORD = "\b\w+b"; private static final String SQL_SPACE = "\s+"; private static final String SQL_OPERATOR = "[=><!]+"; private static final String SQL_NUMBER = "\d+(\.\d*)?"; private static final String SQL_IDENTIFIER = "[azAZ_][azAZ09_]*"; private static final String SQL_QUOTED_IDENTIFIER = "[" + SQL_IDENTIFIER + "]"; private static final String SQL_CHARACTER = "[''"][^'"]*['"]"; private static final String SQL_DATETIME = "\d{4}\d{2}\d{2} \d{2}:\d{2}:d{2}"; private static final String SQL_SYMBOL = ",;()[]{}<>?/\*+=&|%!"; private static final String SQL_WHITESPACE = "[ \t]+"; private static final String SQL_UNKNOWN = "[^\s" + SQL_COMMENT + SQL_STRING + SQL_WORD + SQL_SPACE + SQL_OPERATOR + SQL_NUMBER + SQL_IDENTIFIER + SQL_QUOTED_IDENTIFIER + SQL_CHARACTER + SQL_DATETIME + SQL_SYMBOL + "]"; private static final String SQL_REGEX = SQL_COMMENT + "|" + SQL_STRING + "|" + SQL_WORD + "|" + SQL_SPACE + "|" + SQL_OPERATOR + "|" + SQL_NUMBER + "|" + SQL_IDENTIFIER + "|" + SQL_QUOTED_IDENTIFIER + "|" + SQL_CHARACTER + "|" + SQL_DATETIME + "|" + SQL_SYMBOL; private static final Pattern PATTERN = Pattern.compile(SQL_REGEX); public List<String> tokenize(String input) { List<String> tokens = new ArrayList<>(); Matcher matcher = PATTERN.matcher(input); while (matcher.find()) { tokens.add(matcher.group()); } return tokens; } }
2. 定义语法分析器(Parser)
接下来,需要定义一个语法分析器,用于根据词法分析器生成的词法单元构建SQL语句的抽象语法树(AST),可以使用递归下降解析方法来实现。
import java.util.*; import java.util.stream.*; import org.antlr.v4.*; import org.antlr.v4.runtime.*; import org.antlr.v4.runtime.tree.*; import org.antlr.v4.runtime.tree.ParseTreeWalker; import org.antlr.v4.tool.*; import org.antlr.v4.tool.ast.*; import org.antlr.v4.tool.lexer.*; import org.antlr.v4.tool.parser.*; import org.antlr.v4.tool.tree.*; import org.antlr.v4.tool.grun.*; import org.antlr.v4.*; import org.antlr.v4.runtime.*; import org.antlr.v4.runtime.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr.v4.*; import org.antlr
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