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[FEATURE] How can i replace a Expression #1760
Description
Problem
I want to use JSqlParse to parse some SQL for get formula result;
For example: SELECT CASE WHEN (CASE WHEN 'abcdef' like '%b%e%' THEN 1 ELSE 2 END)>1 THEN 3 ELSE 4 END;
When I implements ExpressionVisitor and override the function visit(CaseExpression caseExpression) ,after I calculated the second CASE WHEN get result is 1 , how can i replace the Expression ' (CASE WHEN 'abcdef' like '%b%e%' THEN 1 ELSE 2 END) ' to new Expression 1。-> SELECT CASE WHEN 1>1 THEN 3 ELSE 4 END;
The JSQLParser has some Function to replace an Expression Node ?
Some Code
public class SelectItemService SelectItemVisitor{
...override
@Override
public void visit(SelectExpressionItem selectExpressionItem){
Expression expression = selectExpressionItem.getExpression();
if (expression instance CaseExpression){
CaseExpression caseExpression = (CaseExpression) expression;
for (WhenClause whenClause : caseExperssion.getWhenClause()){
Expression whenExpression = whenClause.getWhenExpression();
whenExpression.accept(new ExpressionService());
}
}
}
}
public class ExpressionService implements ExpressionVisitor {
...override
@Override
public void visit(CaseExpression caseExpression){
List<WhenClause> whenClauses = caseExpression.getWhenClauses();
for (WhenClause whenClause : whenClauses){
Expression whenExpression = whenClause.getWhenExpression();
if (whenExpression instanceof LikeExpression){
// ignore other visit(....)
whenExpression.accept(this);
String leftExp = ((LikeExpression) whenExpression).getLeftExpression().toString();
String rightExp = ((LikeExpression) whenExpression).getRightExpression().toString();
// here I'm assuming that these two result are the same
// how can i replace the caseExpression to (Expression)LongValue or other Expression？
......
}
}
}
}
Additional context
The used JSQLParser Version: 4.3
Be very grateful
Activity
manticore-projects commentedon Apr 10, 2023
Greetings.
Your
CASEexpression has aWHENclause, holding the secondCASEExpression within aGreaterThanandParenthesis:You can simply replace that second
CASEexpression of theParenthesisby any other Expression.You can generate that AST here.