Data from the client should never be trusted for the client has every possibility to tamper with the data.

validating input in java-44

There are four strategies for validating data, and they should be used in this order: This strategy is also known as "whitelist" or "positive" validation.

The idea is that you should check that the data is one of a set of tightly constrained known good values. Data should be: This strategy, also known as "negative" or "blacklist" validation is a weak alternative to positive validation.

Add this dependency to your // E.g this contract require("This message is bad", contains String("good")); // Will yield this error org.valid4j.exceptions.

Require Violation: expected: a string containing "good" but: was "This message is bad" // E.g this validation validate("This message is bad", contains String("good"), Illegal Argument Exception.class); // Will yield this exception with message // (NOTE: Exception class must accept one String argument in constructor for this feature to be supported)

This is a dangerous strategy, because the set of possible bad data is potentially infinite.

Adopting this strategy means that you will have to maintain the list of "known bad" characters and patterns forever, and you will by definition have incomplete protection.However, there are bad, good and "best" approaches.Often the best approach is the simplest in terms of code.Some documentation and references interchangeably use the various meanings, which is very confusing to all concerned.This confusion directly causes continuing financial loss to the organization.It can take upwards of 90 regular expressions (see the CSS Cheat Sheet in the Development Guide 2.0) to eliminate known malicious software, and each regex needs to be run over every field. Just rejecting "current known bad" (which is at the time of writing hundreds of strings and literally millions of combinations) is insufficient if the input is a string.