JSqlParser使用
时间: 2023-07-11 18:39:10 浏览: 65
JSqlParser是一个Java库,用于解析和分析SQL语句。以下是使用JSqlParser解析SQL语句表名的示例代码:
```java
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;
import net.sf.jsqlparser.JSQLParserException;
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;
import net.sf.jsqlparser.statement.select.SelectBody;
import net.sf.jsqlparser.statement.select.Table;
import net.sf.jsqlparser.statement.select.WithItem;
public class ParseSQL {
public static void main(String[] args) {
String sql = "SELECT * FROM employees e INNER JOIN departments d ON e.department_id = d.department_id WHERE d.department_name = 'Sales'";
try {
Statement statement = CCJSqlParserUtil.parse(new StringReader(sql));
if (statement instanceof Select) {
Select selectStatement = (Select) statement;
SelectBody selectBody = selectStatement.getSelectBody();
if (selectBody instanceof PlainSelect) {
PlainSelect plainSelect = (PlainSelect) selectBody;
List<Table> tables = getTables(plainSelect);
for (Table table : tables) {
String tableName = table.getName();
String aliasName = table.getAlias() != null ? table.getAlias().getName() : null;
System.out.println("Table name: " + tableName);
System.out.println("Table alias: " + aliasName);
}
}
}
} catch (JSQLParserException e) {
e.printStackTrace();
}
}
private static List<Table> getTables(PlainSelect plainSelect) {
List<Table> tables = new ArrayList<>();
tables.addAll(getTablesFromSelectItem(plainSelect.getSelectItems()));
tables.addAll(getTablesFromJoin(plainSelect.getJoins()));
tables.addAll(getTablesFromTable(plainSelect.getFromItem()));
return tables;
}
private static List<Table> getTablesFromSelectItem(List selectItems) {
List<Table> tables = new ArrayList<>();
for (Object selectItem : selectItems) {
if (selectItem instanceof SelectExpressionItem) {
SelectExpressionItem selectExpressionItem = (SelectExpressionItem) selectItem;
if (selectExpressionItem.getExpression() instanceof Column) {
Column column = (Column) selectExpressionItem.getExpression();
Table table = column.getTable();
if (table != null) {
tables.add(table);
}
}
}
}
return tables;
}
private static List<Table> getTablesFromJoin(List joins) {
List<Table> tables = new ArrayList<>();
if (joins == null) {
return tables;
}
for (Object join : joins) {
if (join instanceof Join) {
Join joinExpression = (Join) join;
Table table = joinExpression.getRightItem();
if (table != null) {
tables.add(table);
}
}
}
return tables;
}
private static List<Table> getTablesFromTable(FromItem fromItem) {
List<Table> tables = new ArrayList<>();
if (fromItem instanceof Table) {
Table table = (Table) fromItem;
tables.add(table);
} else if (fromItem instanceof SubSelect) {
SubSelect subSelect = (SubSelect) fromItem;
SelectBody selectBody = subSelect.getSelectBody();
if (selectBody instanceof PlainSelect) {
PlainSelect plainSelect = (PlainSelect) selectBody;
tables.addAll(getTables(plainSelect));
}
} else if (fromItem instanceof LateralSubSelect) {
LateralSubSelect lateralSubSelect = (LateralSubSelect) fromItem;
SubSelect subSelect = lateralSubSelect.getSubSelect();
SelectBody selectBody = subSelect.getSelectBody();
if (selectBody instanceof PlainSelect) {
PlainSelect plainSelect = (PlainSelect) selectBody;
tables.addAll(getTables(plainSelect));
}
} else if (fromItem instanceof ValuesList) {
// do nothing
} else {
throw new UnsupportedOperationException("Unsupported from item: " + fromItem);
}
return tables;
}
}
```
在这个例子中,我们解析了一个SQL查询,该查询涉及两个表:`employees`和`departments`。我们使用JSqlParser解析SQL语句,然后提取表名和表别名。我们首先解析`SELECT`语句,然后获取其`FROM`子句中的所有表。我们从`FROM`子句中提取表,然后从`JOIN`子句和`SELECT`列表中提取表。最后,我们打印出每个表的名称和别名(如果有的话)。