JDBC从SQL查询中解析int

Question

I am pretty new to programming in Java and am having a little difficulty. I have searched around but could not get an exact answer for what I am trying to do.

Basically, I have created a 3-tier application that uses servlets running on a server to access a mySQL database using JDBC.

For the most part, my application runs fine. I am able to run my queries and display my results.

The problem is, I need to implement some logic based on my query, which is a String.

For example,

ex1_query: insert into parts values ('S5', 'P6', 'J7', 50);

ex2_query: insert into parts values ('S5', 'P6', 'J7', 400);

My queries are being submitted through an HTML form as single string. As you can see, the only difference between ex1_query and ex2_query is their last value (50 & 400).

The logic is, that if that last value is >=100, I need to implement some stuff…

If that value is <100, just run the query as specified.

My queries will always be entered in that format, but that last value may vary from 0 - 1000.

So my question is… how can I parse just that last int from the string? So I can determine whether I should or should not implement some specific logic?

I know it sounds pretty simple, but I am having a little trouble. Any help or guidance would be appreciated. Thanks

Answer 1

User Prepared Statement

 String param1= "S5";
  String param2= "p6";
  String param3= "j7"; 
  int param4= 50 0r 400  ; 

 public void someMethod(String param1,String param2,String param3,String param4){

if(param4 >= 100){
//your stuff
param4 =  ; //your new value;
}

query =  insert into parts values (?, ?, ?,?);

And Execute your Query

Answer 2

If you do not have any control about the query you might want to befriend java.util.regex and parse for something like:

"^\s*insert\s+into\s+([A-Za-z0-9]+)\s+values\s+\(\s*('\w+'\s*,\s*){3}([0-9]+)\)\s*$"

This is actually an old-style grep regex but a regex with the same function is possible for java.util.regex. It checks whether the string follows your pattern. submatch #1 should give you your table name. submatch #2-#4 should give you the values 1-3 and submatch #5 contains the number (as string of course) you're looking for. Also a nice way to reject queries you do not like.

Answer 3

But If you don't wanted to go with Preparedstatement

then here is one more option

    String ex1_query = "insert into parts values ('S5', 'P6', 'J7', 50);";

    String lastValue = ex1_query.substring( ex1_query.lastIndexOf(",")+1, ex1_query.lastIndexOf(")")).trim();

 Integer lastNumber = null;
        try {
            lastNumber = Integer.parseInt(lastValue);
        } catch (NumberFormatException e) {
            // if last value is not int then handle here 
            e.printStackTrace();
        } 
        if(lastNumber >=100){

        }

In lastValue you can get 50/400 or any value and do your stuff

Answer 4

If your query will remain same except that integer value, you can use substring .

String query = "insert into parts values ('S5', 'P6', 'J7', 50);"
int value = Integer.parseInt(query.substring(43, query.length()-2));

Or you can use regular expression to accomplish this.

String query = "insert into parts values ('S5', 'P6', 'J7', 50);";
Pattern pattern = Pattern.compile("(?<=(.+,\\s?))(\\d+)(?=(\\);))");
int value = Integer.parseInt(pattern.matcher(query).group());