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2025年05月13日

使用JSQLParser解析和操作SQL

前言

在开发数据库相关应用时，我们常常需要对 SQL 语句进行解析和操作。比如，从复杂的查询语句中提取特定信息，或者动态修改 SQL 语句以满足不同的业务需求。JSQLParser 是一个强大的 Java 库，它允许我们轻松地解析、生成和操作 SQL 语句。

本文将深入探讨如何使用 JSQLParser 实现这些功能，并通过丰富的代码示例进行演示。

介绍

JSQLParser 是一个开源的 Java 库，能够解析各种常见的 SQL 语句，包括 SELECT、INSERT、UPDATE、DELETE 等。它将 SQL 语句解析成一颗抽象语法树（AST），通过对这棵树的遍历和操作，我们可以灵活地提取和修改 SQL 语句中的各个部分。这使得我们在处理复杂 SQL 场景时，无需手动编写繁琐的解析逻辑。

官方：https://jsqlparser.github.io/JSqlParser/usage.html

实现

引入的依赖:

<dependency>
 <groupId>com.github.jsqlparser</groupId>
 <artifactId>jsqlparser</artifactId>
 <version>4.6</version>
</dependency>

SELECT 语句解析

@Test
public void test3(){
 String sql = "SELECT id, name FROM users WHERE age > 30";
 try {
 Statement statement = CCJSqlParserUtil.parse(sql);
 Select selectStatement = (Select) statement;
 // 这里可以对selectStatement进行进一步操作，例如获取SELECT的列、表名、WHERE条件等
 PlainSelect plainSelect = (PlainSelect) selectStatement.getSelectBody();
 System.out.println("SELECT columns: "+ plainSelect.getSelectItems());
 System.out.println("FROM table: " + ((net.sf.jsqlparser.schema.Table) plainSelect.getFromItem()).getName());
 System.out.println("WHERE condition: " + plainSelect.getWhere());
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
SELECT columns: [id, name]
FROM table: users
WHERE condition: age > 30

INSERT 语句解析

@Test
public void test3() {
 String sql = "INSERT INTO users (name, age) VALUES ('John', 30)";
 try {
 // 使用 CCJSqlParserUtil 解析 SQL 语句，将其转换为 Statement 对象
 Statement statement = CCJSqlParserUtil.parse(sql);
 // 判断解析得到的 Statement 对象是否为 Insert 类型
 if(statement instanceof Insert) {
 Insert insert = (Insert) statement;
 // 获取插入的表名
 System.out.println( "Table: " + insert.getTable().getName());
 List<Column> columns = insert.getColumns();
 ExpressionList expressionList = (ExpressionList) insert.getItemsList();
 List<Expression> expressions = expressionList.getExpressions();
 for(int i = 0; i < columns.size(); i++) {
 // 获取插入的列名
 System.out.println("Columns: "+ columns.get(i).getColumnName());
 // 获取插入的值
 System.out.println("Values: "+ expressions.get(i));
 }
 }
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
Table: users
Columns: name
Values: 'John'
Columns: age
Values: 30

UPDATE 语句解析

@Test
public void test3() {
 String sql = "UPDATE users SET age = age + 1 WHERE name = 'John'" ;
 try {
 // 解析 SQL 语句
 Statement statement = CCJSqlParserUtil.parse(sql);
 // 判断是否为 Update 语句
 if (statement instanceof Update) {
 Update update = (Update) statement;
 // 打印要更新的表名
 System.out.println( "Table: "+ update.getTable().getName());
 // 打印更新的列及其更新表达式
 for(UpdateSet updateSet : update.getUpdateSets()) {
 System.out.println("Column: "+ updateSet.getColumns().get(0).getColumnName());
 Expression expression = updateSet.getExpressions().get(0);
 System.out.println( "Value: "+ expression);
 }
 // 打印更新的条件
 System.out.println( "Where: " + update.getWhere());
 }
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
Table: users
Column: age
Value: age + 1
Where: name = 'John'

DELETE 语句解析

@Test
public void test3() {
 String sql ="DELETE FROM users WHERE name = 'John'";
 try {
 Statement statement = CCJSqlParserUtil.parse(sql);
 if(statement instanceof Delete) {
 Delete delete = (Delete) statement;
 String tableName = delete.getTable().getName();
 System.out.println( "Deleting from table: " + tableName);
 Expression whereClause = delete.getWhere();
 if(whereClause!= null) {
 System.out.println("Where condition: " + whereClause);
 }
 }
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
Deleting from table: users
Where condition: name = 'John'

复杂 SQL 案例解析

带 JOIN 的 SELECT 语句解析

@Test
public void test3() {
 String sql ="SELECT a.column1, b.column2 FROM table1 a JOIN table2 b ON a.id = b.id";
 try {
 Statement statement = CCJSqlParserUtil.parse(sql);
 if(statement instanceof Select) {
 Select select = (Select) statement;
 // 获取PlainSelect对象
 PlainSelect plainSelect = (PlainSelect) select.getSelectBody();
 FromItem fromItem = plainSelect.getFromItem();
 System.out.println( "Main table: "+ fromItem);
 List<Join> joins = plainSelect.getJoins();
 for(Join join : joins) {
 System.out.println("Joined table: "+ join.getRightItem());
 Expression onExpression = join.getOnExpression();
 System.out.println( "JOIN condition: "+ onExpression);
 }
 }
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
Main table: table1 a
Joined table: table2 b
JOIN condition: a.id = b.id

嵌套子查询的 SQL 语句解析

@Test
public void test3() {
 String sql ="SELECT a.id, b.name FROM table_a a JOIN table_b b ON a.id = b.table_a_id WHERE a.status = 'active'";
 try {
 Statement statement = CCJSqlParserUtil.parse(sql);
 Select selectStatement = (Select) statement;
 PlainSelect plainSelect = (PlainSelect) selectStatement.getSelectBody();
 System.out.println("SELECT columns: " + plainSelect.getSelectItems());
 System.out.println("FROM table: "+ ((net.sf.jsqlparser.schema.Table) plainSelect.getFromItem()).getName());
 List<Join> joins = plainSelect.getJoins();
 for(Join join : joins) {
 System.out.println( "JOIN table: "+ ((net.sf.jsqlparser.schema.Table) join.getRightItem()).getName());
 System.out.println("JOIN condition: "+ join.getOnExpression());
 }
 System.out.println("WHERE condition: "+ plainSelect.getWhere());
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
SELECT columns: [a.id, b.name]
FROM table: table_a
JOIN table: table_b
JOIN condition: a.id = b.table_a_id
WHERE condition: a.status = 'active'

带有函数嵌套的 SQL 语句解析

@Test
public void test3() {
 String sql ="SELECT UPPER(CONCAT(column1, column2)) FROM table1";
 try {
 Statement statement = CCJSqlParserUtil.parse(sql);
 if(statement instanceof Select) {
 Select select = (Select) statement;
 PlainSelect plainSelect = (PlainSelect) select.getSelectBody();
 SelectItem selectItem = plainSelect.getSelectItems().get(0);
 if (selectItem instanceof SelectExpressionItem){
 Expression expression = ((SelectExpressionItem) selectItem).getExpression();
 if(expression instanceof Function) {
 Function outerFunction = (Function) expression;
 System.out.println("Outer function: " + outerFunction.getName());
 ExpressionList parameters = outerFunction.getParameters();
 if(parameters!= null) {
 List<Expression> paramExpressions = parameters.getExpressions();
 for(Expression paramExpression : paramExpressions) {
 if(paramExpression instanceof Function) {
 Function innerFunction = (Function) paramExpression;
 System.out.println( "Inner function: " + innerFunction.getName());
 System.out.println("Inner function parameters: " + innerFunction.getParameters());
 }
 }
 }
 }
 }
 }
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
Outer function: UPPER
Inner function: CONCAT
Inner function parameters: column1, column2

语句修改

@Test
public void test3() {
 String SQL ="SELECT DISTINCT u.id, r.role_name, u.user_name, u.sex, u.email " +
 "FROM t_user u " + "LEFT JOIN t_role r ON u.role_id = r.id "+
 "WHERE r.role_name = '管理员' "+
 "ORDER BY u.age DESC "+
 "LIMIT 0,10";
 try {
 Select select = (Select) CCJSqlParserUtil.parse(SQL);
 PlainSelect plainSelect = (PlainSelect) select.getSelectBody();
 System.out.println( "【DISTINCT 子句】：" + plainSelect.getDistinct());
 System.out.println( "【查询字段】：" + plainSelect.getSelectItems());
 System.out.println("【FROM 表】：" + plainSelect.getFromItem());
 System.out.println("【WHERE 子句】：" + plainSelect.getWhere());
 System.out.println("【JOIN 子句】：" + plainSelect.getJoins());
 System.out.println( "【LIMIT 子句】：" + plainSelect.getLimit());
 System.out.println("【OFFSET 子句】：" + plainSelect.getOffset());
 System.out.println("【ORDER BY 子句】：" + plainSelect.getOrderByElements());
 System.out.println( "--------------------------------------------------------");
 // 取消去重
 plainSelect.setDistinct(null);
 // 修改查询字段为 *
 List<SelectItem> selectItems = new ArrayList<>();
 selectItems.add(new AllColumns());
 plainSelect.setSelectItems(selectItems);
 // 修改 WHERE 子句
 EqualsTo equalsTo = new EqualsTo();
 equalsTo.setLeftExpression(new Column("u.id"));
 equalsTo.setRightExpression(new LongValue(1));
 plainSelect.setWhere(equalsTo);
 // 修改 LIMIT 子句
 Limit limit = new Limit();
 limit.setRowCount(new LongValue(5));
 limit.setOffset(new LongValue(0));
 plainSelect.setLimit(limit);
 // 修改排序为 u.age ASC
 OrderByElement orderByElement = new OrderByElement();
 orderByElement.setExpression(new Column("u.age"));
 orderByElement.setAsc(true ); // 升序
 plainSelect.setOrderByElements(Collections.singletonList(orderByElement));
 System.out.println("【处理后 SQL】"+ plainSelect);
 } catch (JSQLParserException e) {
 e.printStackTrace();
 }
}
 
 
【DISTINCT 子句】：DISTINCT
【查询字段】：[u.id, r.role_name, u.user_name, u.sex, u.email]
【FROM 表】：t_user u
【WHERE 子句】：r.role_name = '管理员'
【JOIN 子句】：[LEFT JOIN t_role r ON u.role_id = r.id]
【LIMIT 子句】： LIMIT 0, 10
【OFFSET 子句】：null
【ORDER BY 子句】：[u.age DESC]
--------------------------------------------------------
【处理后 SQL】SELECT * FROM t_user u LEFT JOIN t_role r ON u.role_id = r.id WHERE u.id = 1 ORDER BY u.age LIMIT 0, 5

最后

在实际项目中，JSQLParser可以应用于代码生成、SQL语句优化、语法验证以及多数据库兼容性处理等多个方面。掌握JSQLParser的使用方法，能够帮助开发人员更加高效地处理与数据库交互的逻辑，提高应用程序的质量和性能。

标签：javaconditionparser 

作者:alicucu , 分类:技术文章 , 浏览:11 , 评论:0

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