Java - How to set a String dynamically during runtime

Question

I have to build an SQL query where I have to replace two params in the String.

The String variable CLEAN_CSV_PATH which represents a path
The String variable LINES_TERMINATED_OS which represents a the escape character \r\n that are needed for windows or linux, depends.

The params are provided during Main execution with the Scanner class.

This is my SQL String :

private static String LOAD_ALL_ALIASES = //

        "LOAD DATA LOCAL INFILE '" + CLEAN_CSV_PATH + "' INTO TABLE plantbiocore.Alias " //
                + "FIELDS TERMINATED BY ',' " //
                + "OPTIONALLY ENCLOSED BY  '\"' "
                + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
                + "IGNORE 1 LINES " //
                + "(locus_id, organism_id, variable, alias) "; //



 Scanner scanner = new Scanner(System.in);
 CLEAN_CSV_PATH = scanner.next() // Here the CLEAN_CSV_PATH does not appear in my LOAD_ALL_ALIASES

niemar · Accepted Answer · 2018-02-22 12:56:48Z

1

What you need is called PreparedStatement in java. Google it, there are many examples of using this class. The other problem is that you are setting CLEAN_CSV_PATH after you used it to set LOAD_ALL_ALIASES. It can't work in Java.

answered Feb 22, 2018 at 12:56

niemar

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Comments

davidxxx · Accepted Answer · 2018-02-22 13:07:31Z

You need to do the things in the reverse way.
First set CLEAN_CSV_PATH with the scanner. Then resolve your String with.
To allow to create queries with different CLEAN_CSV_PATH, you could extract it into a method that accepts a parameter.

public void foo(){
   Scanner scanner = new Scanner(System.in);
   String csvPath = scanner.next()
   String query = getQuery(csvPath);         
   // ...
}

private static String getQuery(String csvPath){

       return "LOAD DATA LOCAL INFILE '" + csvPath + "' INTO TABLE plantbiocore.Alias " //
                + "FIELDS TERMINATED BY ',' " //
                + "OPTIONALLY ENCLOSED BY  '\"' "
                + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
                + "IGNORE 1 LINES " //
                + "(locus_id, organism_id, variable, alias) "; //
}

Note that LINES_TERMINATED_OS could be replaced by System.lineSeparator() that returns at runtime the OS dependent line separator.

Morchul · Accepted Answer · 2018-02-22 13:01:07Z

0

Write it in the right sequence then it will work fine:

    String LOAD_ALL_ALIASES;
    String CLEAN_CSV_PATH;
    String LINES_TERMINATED_OS;

    Scanner scanner = new Scanner(System.in);
    CLEAN_CSV_PATH = scanner.next();
    LINES_TERMINATED_OS = scanner.next();

    LOAD_ALL_ALIASES = "LOAD DATA LOCAL INFILE '" + CLEAN_CSV_PATH + "' INTO TABLE plantbiocore.Alias " //
            + "FIELDS TERMINATED BY ',' " //
            + "OPTIONALLY ENCLOSED BY  '\"' "
            + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
            + "IGNORE 1 LINES " //
            + "(locus_id, organism_id, variable, alias) ";

answered Feb 22, 2018 at 13:01

Morchul

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