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The easiest way to parse SQL in Java is by using an existing open-source library rather than writing a parser from scratch. Building your own parser using tools like StringTokenizer or regular expressions fails quickly because SQL syntax contains complex features like nested subqueries, joins, and dialect-specific keywords.

The most widely accepted, pure-Java approach for this task is JSqlParser. Why Use JSqlParser?

Zero Database Connection Needed: It parses SQL strictly as text strings, meaning you don’t need an active database connection to evaluate a query.

Deconstructs Queries: It translates plain text SQL strings into a navigable hierarchy of Java objects (an Abstract Syntax Tree).

Modifiable AST: You can read, modify, or completely generate new SQL statements programmatically. Step-by-Step Implementation 1. Add the Dependency

Add the library to your project. If you are using Maven, place this snippet into your pom.xml file:

com.github.jsqlparser jsqlparser 4.9 Use code with caution. 2. Parse a Simple SELECT Statement

You can extract individual columns, the target table, and specific conditions using the CCJSqlParserUtil helper class.

import net.sf.jsqlparser.parser.CCJSqlParserUtil; import net.sf.jsqlparser.statement.Statement; import net.sf.jsqlparser.statement.select.PlainSelect; import net.sf.jsqlparser.statement.select.Select; public class SqlParserDemo { public static void main(String[] args) { String sql = “SELECT id, name, age FROM users WHERE age > 21”; try { // Parse the plain SQL string into a Statement object Statement statement = CCJSqlParserUtil.parse(sql); // Check if the statement is a SELECT query if (statement instanceof Select) { Select selectStatement = (Select) statement; PlainSelect plainSelect = (PlainSelect) selectStatement.getSelectBody(); // 1. Get the target table System.out.println(“Table: ” + plainSelect.getFromItem()); // Output: Table: users // 2. Get the requested columns System.out.println(“Columns: ” + plainSelect.getSelectItems()); // Output: Columns: id, name, age // 3. Get the WHERE condition clause System.out.println(“Where clause: ” + plainSelect.getWhere()); // Output: Where clause: age > 21 } } catch (Exception e) { System.err.println(“Failed to parse invalid SQL syntax: ” + e.getMessage()); } } } Use code with caution. 3. Modify an Existing Query Programmatically SQL parser library for Java – Stack Overflow