Develop Reference

How to compare LocalDateTime values in JPQL query?

It is necessary to select dataset using JPQL query with optional condition - comparing the field value (LocalDateTime type) with a user-specified parameter (also LocalDateTime type).
First I made a well working code:
return entityManager.createQuery(
"SELECT new com.******.*******.*******.****.models.dto.SomeDto " +
"(s.id, " +
"s.userId) " +
"s.persistDate) " +
"FROM Some s WHERE s.userId = :userId
AND s.persistDate >= :userDateTime", SomeDTO.class)
.setParameter("userId", userId)
.setParameter("userDateTime", userDateTime)
This code works but there is one problem:
this condition may exist or may not exist - dependent on app logic. Therefore, there is a need not to use injection using .setParameter (for this condition), but to form a string (which may be empty) depending on the logic and then add to the request:
String extraCondition = (userDateString.equals("false")) ? "" :
"AND s.persistDateTime >= " + userDateString;
return entityManager.createQuery(
"SELECT new com.******.*******.*******.****.models.dto.SomeDto " +
"(s.id, " +
"s.userId) " +
"s.persistDate) " +
"FROM Some s WHERE s.userId = :userId " + extraCondition, SomeDTO.class)
.setParameter("userId", userId)
But the problem is that no matter how I tried to format the userDateString variable, I get an Internal Server Error.I even tried using just a text string instead of variable (tried with different formatting):
String extraCondition = (userDateString.equals("false")) ? "" :
"AND s.persistDateTime >= 2023-01-27T23:30:50";
But the result is also bad - Internal Server Error.
I also tried using the .isAfter method instead of the ">=" operator, but that didn't help either.
How to inject LocalDateTime values comparing into query as String?

even if the date string may or may not be necesssary, you can (and should!) still use parameter injection, not formatted values.
Basically, your code should look like this:
String queryStr = ....;
boolean someCondition = <expensive_test_here>;
if(someCondition) {
queryStr += " AND s.persistDate >= :userDateTime";
}
Query q = em.createQuery(queryStr).setParameter("userId", userId);
if(someCondition) {
q.setParameter("userDateTime", userDateTime);
}

use jpa nativequery multiple columns in object list array

Use jpa nativequery multiple columns in object list array
List<Object []> queryList = new ArrayList<>();
String[] arr = {"val1", "val2"};
queryList.add(arr);
String sql = SELECT * FROM TABLE A WHERE (A.COL1, A.COL2) IN (:queryList)
Query query = entityManager.createNativeQuery(sql);
query.setParameter("queryList", queryList);
In postgresql like this
SELECT * FROM TABLE A WHERE (A.COL1, A.COL2) IN (('val1', 'val2'), ('val3', 'val4'));
Here is the Exception
Caused by: org.postgresql.util.PSQLException: ERROR: operator does not exist: record = bytea
建議：No operator matches the given name and argument types. You might need to add explicit type
Is this possible?

I would try to restructure the query as follows:
SELECT * FROM TABLE A
WHERE (A.COL1 = 'val1' and A.COL2 = 'val2')
OR (A.COL1 = 'val3' and A.COL2 = 'val4')
This would allow the query to be constructed as follows:
List<String[]> queryList = new ArrayList<>();
String[] arr = {"val1", "val2"};
String[] arr = {"val3", "val4"};
queryList.add(arr);
String sql = "SELECT * FROM TABLE A "; //dont forget space at end
if (!queryList.isEmpty()){
sql = sql + "WHERE "; //dont forget space at end
for (String[] queryParam : queryList ){
sql = sql + " (A.COL1 = '"+ queryParam[0] + "' and A.COL2 = '" + queryParam[1] + "') OR "; //dont forget space at end and simple colons for param
}
//finally remove the last OR.
Integer indexLastOR = sql.lastIndexOf("OR");
sql = sql.substring(0, indexLastOR);
}
Query query = entityManager.createNativeQuery(sql);
This will also allow the query to be implemented without being native, which is advisable to maintain the JPA philosophy.

noob, java spring autowired hibernate mysql query, is this right?

I'm working on a small program that lists local train stops in a numbered list then asks for the user to type the number of the station that they wish to see the next arrival time for.
The problem I have is I don't think the MySQL query is correct to retrieve the arrival time. The list returns empty. Using jdbc previously, this query worked fine:
"SELECT arrival_time FROM stop_times WHERE stop_id = '"
+ myStation.getID()
+ "' AND arrival_time > time('now', 'localtime') ORDER BY arrival_time asc;";
And the current hibernate query:
public List<String> getArrivals() {
sessionFactoryBean.getCurrentSession().beginTransaction();
String sql = "SELECT arrival_time FROM stop_times WHERE stop_id = '"
+ myStation.getID()
+ "' AND arrival_time > time('now', 'localtime') ORDER BY arrival_time asc;";
Query query = sessionFactoryBean.getCurrentSession()
.createSQLQuery(sql)
.addEntity(Station.class);
List<String> arrivals = query.list();
sessionFactoryBean.getCurrentSession().getTransaction().commit();
return arrivals;
}
Called from this method and where I get IndexOutOfBoundsException:
public String getNextArrival(int user_input) {
getStationName(user_input);
List<String> arrivals1 = arrival.getArrivals();
System.out.println(arrivals1);
System.out.println(arrivals1.size());
String arrivalTime = arrivals1.get(user_input);
return convertTime(arrivalTime);
}
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0,
Size: 0
at java.util.ArrayList.rangeCheck(ArrayList.java:653)
at java.util.ArrayList.get(ArrayList.java:429)
at com.moeller.code.Stops.getNextArrival(Stops.java:73)
Line 73 String arrivalTime = arrivals1.get(user_input);'
The DataBase is stored locally.

There are several problems with this.
First, the query does not use parameters, which means you will likely make this mistake elsewhere where it will be a danger. You have to pass on variables like this:
String sql = "SELECT arrival_time FROM stop_times WHERE stop_id = ?"
+ " AND arrival_time > time('now', 'localtime') ORDER BY arrival_time asc;";
Query query = sessionFactoryBean.getCurrentSession()
.createSQLQuery(sql)
.addEntity(Station.class);
query.setParameter(1, myStation.getID());
See the question mark? That is a positional parameter. You can also use named parameters.
String sql = "SELECT thing FROM table WHERE column1 LIKE :ptrn";
...
query.setParameter("ptrn", "%that%");
Notice how inside the query the parameter starts with :, but it does not when calling setParameter.
This way of safely inserting parameters is called using "Prepared Statements", or "Parameterized Queries". Find a quick tutorial on them, they are very important.
Secondly, in getNextArrival you forget to check if the list has that many elements.
if (arrivals1.size() <= user_input) {
return null;
}
Of course then you have to be careful when it returns a null to the function where it's used.

You are using a wrong method for the List.
when yo use List.get(param) param should be the position that you are looking for, no the userInput.
you need loop the list and compare each position of the list with the user input.
best Regards

sql query does not give results

I am facing some issue with the following query.
for (String string : projects) {
String sql = "SELECT eff.id,eff.taskNo,eff.projectId,sum(eff.hours),eff.employeeId FROM EffortCalculator eff where eff.projectId='"
+ string + "' and eff.dayDate >= '2014-12-15' and eff.dayDate <= '2014-12-16' GROUP BY eff.projectId";
System.out.println("sql" + sql);
SQLQuery query = session.createSQLQuery(sql);
System.out.println(query.list());
// query.addEntity(EffortCalculator.class);
list.addAll(query.list());
}
When I execute this query in MySQL DB it works fine. It actually contains two rows. But when I use this query in hibernate it gives empty list.

java - how to inject custom PreparedStatement's paramters

I am trying to implement PreparedStatement, which won't work with sql DB.
Suppose I have the following sql query:
String selectSqlQuery = "SELECT * FROM customer WHERE f1 = ? AND f2 =? AND f3 > ?";
and the following code:
//----
prest = con.prepareStatement(selectSqlQuery );
prest.setString(1, "val1");
prest.setString(2, "val2");
prest.setInt(3, 108);
ResultSet rs = prest.executeQuery();
//---
My question is how to implement setString and setInt methods for injecting params?
For now I save parameters' indexes and values into HashMap, but after it I can't make injection into sql query string.

implementation of sql's java interfaces are part of vendor specific jdbc driver. You probably just need to get the proper jdbc jar file for you database. writing implementations of such stuff is usually just needed if you intend to write your own database driver...

Since you're writing your own driver, you can play with your class a little. Let's change the approach. If you have a query like this one:
"SELECT * FROM table WHERE id = ? AND name = ?"
Replace the ? to turn it into
"SELECT * FROM table WHERE id = {0} AND name = {1}"
About your set methods, those will have to save your new parameters in an Object array, again matching against the index.
Object parameterArray = new Object[1];
public boolean setString(int paramIndex, String param) {
if(paramIndex < 0 || paramIndex > parameterArray.length)
throw new IllegalArgumentException("Can't set parameter " + paramIndex + ", The query only has " + parameterArray.length + " parameters.");
parameterArray[paramIndex - 1] = param;
}
Before executing the query, take advantage of your formatted string and set the parameters:
MessageFormat messageFormat = new MessageFormat(query);
String newQuery = messageFormat.format(parameterArray);
The format method will replace the {number} substrings for the corresponding element in the index represented by the number between brackets.