AbstractJsqlParser是在什么时候处理
时间: 2023-12-17 19:05:43 浏览: 11
AbstractJsqlParser是在解析SQL语句时处理的。它是一个Java库,用于将SQL语句解析成语法树,从而使开发人员能够更轻松地处理和分析SQL语句。它可以解析各种SQL语句,包括SELECT、INSERT、UPDATE和DELETE语句,还可以处理子查询、JOIN条件和函数等复杂的SQL语句。
相关问题
AbstractJsqlParser
AbstractJsqlParser is a Java library for parsing and analyzing SQL statements. It provides a simple and easy-to-use interface for developers to parse and analyze SQL statements without having to write complex parsing code themselves.
The library supports a wide range of SQL dialects including MySQL, Oracle, PostgreSQL, SQL Server, DB2, SQLite, and more. It can parse both simple and complex SQL statements, including SELECT, INSERT, UPDATE, DELETE, CREATE, ALTER, and DROP statements.
AbstractJsqlParser provides a robust and extensible parsing framework that allows developers to easily add custom parsing rules and support for new SQL dialects. It also includes a number of built-in features such as SQL syntax validation, SQL statement normalization, and SQL statement type detection.
Overall, AbstractJsqlParser is a powerful and flexible library that simplifies the process of parsing and analyzing SQL statements in Java applications.
mybatisplus 分页重写count方法
MyBatis-Plus是一个基于MyBatis的增强工具,提供了很多便捷的功能,其中包括分页查询。在使用MyBatis-Plus进行分页查询时,可以通过重写count方法来实现自定义的分页查询逻辑。
要重写count方法,需要创建一个自定义的分页拦截器,并在该拦截器中实现count方法的重写。以下是一个示例:
```java
public class CustomPaginationInterceptor extends PaginationInterceptor {
@Override
public boolean optimizeCountSql() {
return false; // 关闭内置的 count 查询
}
@Override
public List<ISqlParser> getSqlParserList() {
List<ISqlParser> sqlParserList = super.getSqlParserList();
sqlParserList.add(new CustomCountSqlParser()); // 添加自定义的 count 查询解析器
return sqlParserList;
}
public static class CustomCountSqlParser extends AbstractJsqlParser {
@Override
public SqlInfo parser(MetaObject metaObject, String sql) {
MappedStatement mappedStatement = PluginUtils.getMappedStatement(metaObject);
if (SqlCommandType.SELECT == mappedStatement.getSqlCommandType()) {
// 判断是否为 count 查询
if (sql.trim().toLowerCase().matches("^select\\s+count\\(.+")) {
// 自定义 count 查询逻辑
String newSql = "SELECT COUNT(1) FROM (" + sql + ") tmp";
return SqlInfo.newInstance().setSql(newSql);
}
}
return null;
}
}
}
```
在上述示例中,我们创建了一个自定义的分页拦截器`CustomPaginationInterceptor`,并重写了`optimizeCountSql`方法,将内置的count查询关闭。然后,我们添加了一个自定义的count查询解析器`CustomCountSqlParser`,在该解析器中实现了自定义的count查询逻辑。
使用自定义的分页拦截器后,可以在MyBatis-Plus的分页查询中使用自定义的count查询逻辑。
相关推荐
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![pptx](https://img-home.csdnimg.cn/images/20210720083543.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)