CODEWITHSUNDEEP
javajspjakarta-ee
magicianiam
magicianiam

Reputation: 1579

Checking if string is null when string is declared using request.getParameter in java

I'm trying to check if the string i declared using request.getParameter is null or empty.

But i keep getting an error when i tried doing this code: the error is nullexception error.

<%
String name = request.getParameter("name");
String acctnum = request.getParameter("acctnum");
String pin = request.getParameter("pin");
String balance = request.getParameter("balance");
out.println(name+acctnum+pin+balance);
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/jsp", "root", "");

String sql = "Insert into users(name, account_numer, pin, balance) values('"+name+"',     '"+acctnum+"', '"+pin+"', '"+balance+"')";
Statement stmt = conn.createStatement();
stmt.execute(sql);

conn.close();
if(name != null){
response.sendRedirect("index.jsp");
}

} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
%>

i also tried .equals("") but to no avail.

What i am doing wrong here, i want to check whether the string is empty or null to prevent it form redirecting to another page.

Thank you

Upvotes: 0

Views: 7919

Answers (2)

user2030471
user2030471

Reputation:

I believe you're getting the exception before you reach if(name != null). You are using the parameters while initializing the sql variable. Are you expecting null strings to be present while doing that?

I think you should have a null check before doing any DB related operation:

if (nullChecksPassed) {
    Class.forName("");
    Connection conn = DriverManager.getConnection("");
    String sql = "";
    Statement stmt = conn.createStatement();
    stmt.execute(sql);
    conn.close();
}
if (name != null) {
    response.sendRedirect("index.jsp");
}

Upvotes: 2

npinti
npinti

Reputation: 52185

It might be worth checking out Apache's StringUtils class, more specifically the isEmpty(String str) method:

public static boolean isEmpty(String str) Checks if a String is empty ("") or null.

StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false

NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().

Parameters: str - the String to check, may be null

Returns: true if the String is empty or null

Also, you might want to use prepared statements for your SQL queries. The one you have is prone to SQL injection.

Upvotes: 2

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