1. Communicating with Databases
String based queries are prevalent:
JPA, Hibernate, TopLink
Strings
JAVA DB

2. Example: Using JPA to query DB
Query in JPA Query Language:
“SELECT w FROM Weblog w
WHERE w.id = ?1 AND w.link.id = ?2”
Java syntax in query String
Mapping Java Classes to DB Tables:
Expressed in Object Relational Mapping (ORM)

3. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

4. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string

5. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string
Create query

6. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string
Create query
Set parameters

7. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string
Create query
Set parameters

8. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string
Create query
Set parameters
Execute query

9. Example: Using JPA to query DB
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Build query string
Create query
Set parameters
Execute query
Efficient
Flexible
Unsafe

10. Uncaught Errors String getText(String id, Link link) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

11. Uncaught Errors String getText(String id, Link link) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
// q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

12. Uncaught Errors Unset parameter String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
// q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter

13. Uncaught Errors Unset parameter String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter

14. Uncaught Errors Unset parameter Unsafe param type
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, new Weblog());
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type

15. Uncaught Errors Unset parameter Unsafe param type
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type

16. Uncaught Errors Unset parameter Unsafe param type Unsafe downcast
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Warranty w = (Warranty) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type
Unsafe downcast

17. Uncaught Errors
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type
Unsafe downcast
Java compiler does not reason about the query strings; cannot typecheck.

18. Refactor: Weblog.id  Weblog.name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type
Unsafe downcast

19. Refactor: Weblog.id  Weblog.name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Refactor
Unset parameter
Unsafe param type
Unsafe downcast
Don’t Refactor
Need to know type of w and w.link to refactor safely.

20. Refactor: Weblog.id  Weblog.name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type
Unsafe downcast
Refactoring difficult

21. String Based Query Challenges
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Unset parameter
Unsafe param type
Unsafe downcast
Refactoring difficult

22. Deep Typechecking Example
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Query safety:
All params set
Params safely set
Result safely downcast
Is this query exec safe?
Need to know:
query string
param types

23. Deep Typechecking Example
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Bound Query:
query string
param types
Example :
query : “SELECT … ?1 … ?2 … ?3 …”
?1 : String
?2 : Weblog
?3 : unknown
At each program point map each var to a set of BQs.

24. Bound Query Analysis String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

25. Bound Query Analysis qStr = “SELECT … ?2”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”

26. Bound Query Analysis qStr = “SELECT … ?2”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”

27. Bound Query Analysis qStr = “SELECT … ?2”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”

28. Bound Query Analysis qStr = “SELECT … ?2” query : “SELECT …”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”
query : “SELECT …”
?1 : unknown
?2 : unknown

29. Bound Query Analysis qStr = “SELECT … ?2” query : “SELECT …”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”
query : “SELECT …”
?1 : unknown
?2 : unknown
query : “SELECT …”
?1 : String
?2 : unknown

30. Bound Query Analysis qStr = “SELECT … ?2” query : “SELECT …”
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
qStr = “SELECT … ?2”
query : “SELECT …”
?1 : unknown
?2 : unknown
query : “SELECT …”
?1 : String
?2 : unknown
query : “SELECT …”
?1 : String
?2 : int

31. Bound Query Analysis Checking param types: Parse query string
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Checking param types:
Parse query string
Check all params set
Check param types
Bound Queries:
query : “SELECT …”
?1 : String
?2 : int

32. Bound Query Analysis Checking result type: Infer result type
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
Checking result type:
Infer result type
Propagate result type
Check downcasts
Bound Queries:
query : “SELECT …”
?1 : String
?2 : int
result : Weblog
query : “SELECT …”
?1 : String
?2 : int

33. Bound Query Analysis
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
If a query passes Deep Typechecking, then it will not cause an error at runtime.
Therefore, Bound Query Analysis has no silent failures.

34. Deep Refactoring Example
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

35. Deep Refactoring Example
Refactor Weblog field:
id  name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

36. Deep Refactoring Example
Refactor Weblog field:
id  name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

37. Deep Refactoring Example
Refactor Weblog field:
id  name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

38. Deep Refactoring Example
Refactor Weblog field:
id  name
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
query :
SELECT w FROM Weblog w
WHERE w.id = ?1
AND w.link.id = ?2
?1 : String
?2 : int

39. Deep Refactoring Example
Refactor Weblog field:
id  name
Refactor full query
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
query :
SELECT w FROM Weblog w
WHERE w.id = ?1
AND w.link.id = ?2
?1 : String
?2 : int

40. Deep Refactoring Example
Refactor Weblog field:
id  name
Refactor full query
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
query :
SELECT w FROM Weblog w
WHERE w.name = ?1
AND w.link.id = ?2
?1 : String
?2 : int

41. Deep Refactoring Example
Refactor Weblog field:
id  name
Refactor full query
Propagate changes
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
query :
SELECT w FROM Weblog w
WHERE w.name = ?1
AND w.link.id = ?2
?1 : String
?2 : int

42. Deep Refactoring Example
Refactor Weblog field:
id  name
Refactor full query
Propagate changes
String getText(String id, Link link) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.name = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }
query :
SELECT w FROM Weblog w
WHERE w.name = ?1
AND w.link.id = ?2
?1 : String
?2 : int

43. Flow Sensitivity String getText(String id, Link link) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

44. Flow Sensitivity String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

45. Flow Sensitivity String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

46. Flow Sensitivity String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;

47. Flow Sensitivity String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;

48. Flow Sensitivity String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;

49. Flow Sensitivity qStr = “SELECT … ?2”
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;

50. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int

51. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int
qStr = “SELECT … ?1”

52. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int
qStr = “SELECT … ?1”

53. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int
qStr = “SELECT … ?1”

54. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int
qStr = “SELECT … ?1”
query : “SEL … ?1”
?1 : String

55. Flow Sensitivity qStr = “SELECT … ?2” query : “SEL … ?2” ?1 : String
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
query : “SEL … ?2”
?1 : String
?2 : int
qStr = “SELECT … ?1”
query : “SEL … ?1”
?1 : String
“SEL … ?2”
?1 : String
?2 : int
“SEL … ?1”

56. Flow Sensitivity As before, for each bound query: Check param types
String getText(String id, Link link) {
String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
if(link != null) {
qStr += “AND w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
} else { }
Weblog w = (Weblog) q.execQuery();
return w.text;
As before, for each bound query:
Check param types
Check result type
In general, we express Bound Query Analysis as a dataflow analysis.
“SEL … ?2”
?1 : String
?2 : int
“SEL … ?1”

57. Loops String getText(String id, Link link) { String qStr; Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “OR w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

58. Loops String getText(String id, List<Link> links) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “OR w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

59. Loops String getText(String id, List<Link> links) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
qStr += “OR w.link.id = ?2”;
q = createQuery(qStr);
q.setParam(1, id);
q.setParam(2, link.id);
Weblog w = (Weblog) q.execQuery();
return w.text; }

60. Loops String getText(String id, List<Link> links) { String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
for(int i = 0; i < links.size(); i++) {
qStr += “ OR w.link.id = ?” + i; }
q = createQuery(qStr);
...

61. Loops qStr = ??? qStr = “SELECT … w.id = ?1” ( “ OR w.link.id = ?#” )*
String getText(String id, List<Link> links) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
for(int i = 0; i < links.size(); i++) {
qStr += “ OR w.link.id = ?” + i; }
q = createQuery(qStr);
...
qStr =
“SELECT … w.id = ?1”
( “ OR w.link.id = ?#” )*
qStr = ???

62. Loops qStr = “SELECT … w.id = ?1” ( “ OR w.link.id = ?#” )*
String getText(String id, List<Link> links) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
for(int i = 0; i < links.size(); i++) {
qStr += “ OR w.link.id = ?” + i; }
q = createQuery(qStr);
...
qStr =
“SELECT … w.id = ?1”
( “ OR w.link.id = ?#” )*

63. Loops qStr = “SELECT … w.id = ?1” ( “ OR w.link.id = ?#” )*
Deep Refactoring:
know query structure
know fragment locs
refactor across loops
String getText(String id, List<Link> links) {
String qStr;
Query q;
qStr = “SELECT w FROM Weblog w ”;
qStr += “WHERE w.id = ?1 ”;
for(int i = 0; i < links.size(); i++) {
qStr += “ OR w.link.id = ?” + i; }
q = createQuery(qStr);
...
Deep Typechecking:
unknown # of params
do not check params
can still check result
qStr =
“SELECT … w.id = ?1”
( “ OR w.link.id = ?#” )*

64. Multiple Methods String Analysis : interprocedural compute regexps
Bound Query Analysis :
intraprocedural
no complex aliasing
Result Analysis :
propagate result type
String mainQueryStr() {
return “SELECT ... ?1”; }
Object getMain() {
String qStr = mainQueryStr();
Query q = createQuery(qStr);
q.setParam(1, “main”);
return q.execQuery();
String mainId() {
return ((Weblog) getMain()).id;