java打印出一个arraylist来构建一个SQL字符串

Question

I am trying to build a SQL statement using a set of values from an array list. I'll start from the beginning.

Define my arrayList

ArrayList<String[]> myRecords = new ArrayList<String[]>();

Define my array string:

String[] record = new String[2];

Then i loop though a file and split on on the comma and add the record to myRecords

while(scan.hasNext())
        {
            record = scan.nextLine().split(",");
            myRecords.add(record);
        }

So now I need to create an SQL import statement and use thoes values in the arraylist. For example.

String sql = "insert into table (parm1, parm2) Values ";

Now I want to loop though the array and put fill in param1 & param2.

   for(String[] list : myRecords)
    {
       sqlString +=("(");
        for(String list1 : list)
        {
            sqlString +=("'"+ list1+ "',");
        }
        sqlString+=("),");
    }
        sqlString += ';';

    logger.info(sqlString);

The problem now is when I print out the SQL string it looks like this.

insert into table (parm1, parm2) Values ('value1','value2',),('value3','value4',),;

So on and so forth.

So the problem is that there is an extra comma in there at the end of value2 and value4. And after the last bracket before the ; I've gone switching it around etc, but I can't seem to figure out how i can get a proper formatted sql string.

This is how it should look.

 insert into table (parm1, parm2) Values ('value1','value2'),('value3','value4');

Perhaps it's the way I am forming my for loop. Any suggestions would be great!

Answer 1

Add a counter and initialize it to 0, increment the counter after added a value. Only append the comma when the counter is larger than 0

int recCount = 0;
for(String[] list : myRecords)
{
    if (recCount > 0)
    {
        sqlString += ",";
    }
    sqlString +=("(");
    int count = 0
    for(String list1 : list)
    {
        if (count > 0)
        {
            sqlString += ",";
        }
        sqlString += "'"+ list1+ "'";
        count++;
    }
    sqlString+=(")");
    recCount++;
}

Building SQL strings in general is not a great idea and is a major security risk

Answer 2

Simply:

boolean first = true;
for(String[] list : myRecords) {
    if(first) {
        first = false;
    } else {
        sqlString += ',';
    }
    sqlString +=("(");
    for(String list1 : list) {
        sqlString +=("'"+ list1+ "',");
    }
    sqlString+=(")");   // no more "'"
}
sqlString += ';';