An API is a contract between a caller and a callee. The most common forms of API abuse are caused by the caller failing to honor its end of this contract. For example, if a program fails to call chdir() after calling chroot(), it violates the contract that specifies how to change the active root directory in a secure fashion. Another good example of library abuse is expecting the callee to return trustworthy DNS information to the caller. In this case, the caller abuses the callee API by making certain assumptions about its behavior (that the return value can be used for authentication purposes). One can also violate the caller-callee contract from the other side. For example, if a coder subclasses SecureRandom and returns a non-random value, the contract is violated.
Often Misused: Boolean.getBoolean()
Boolean.getBoolean() is often confused with Boolean.valueOf() or Boolean.parseBoolean() method calls.Boolean.getBoolean() is often misused as it is assumed to return the boolean value represented by the specified string argument. However, as stated in the Javadoc Boolean.getBoolean(String) method "Returns true if and only if the system property named by the argument exists and is equal to the string 'true'."Most often what the developer intended to use was a call to
Boolean.valueOf(String) or Boolean.parseBoolean(String) method.Example 1: The following code will not behave as expected. It will print "FALSE" as
Boolean.getBoolean(String) does not translate a String primitive. It only translates system property.
...
String isValid = "true";
if ( Boolean.getBoolean(isValid) ) {
System.out.println("TRUE");
}
else {
System.out.println("FALSE");
}
...