In this example, the expression in the if statement compares the class of the inputClass object to a trusted class by comparing the class names.
However, multiple classes can have the same name therefore comparing an object's class by name can allow untrusted classes of the same name as the trusted class to be use to execute unintended or incorrect code. To compare the class of an object to the intended class the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.
BadJava
if (inputClass.getClass().getName().equals("TrustedClassName")) { // Do something assuming you trust inputClass // ... }
In this example, the expression in the if statement compares the class of the inputClass object to a trusted class by comparing the class names.
However, multiple classes can have the same name therefore comparing an object's class by name can allow untrusted classes of the same name as the trusted class to be use to execute unintended or incorrect code. To compare the class of an object to the intended class the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.
GoodJava
if (inputClass.getClass() == TrustedClass.class) { // Do something assuming you trust inputClass // ... }
In this example, the Java class, TrustedClass, overrides the equals method of the parent class Object to determine equivalence of objects of the class. The overridden equals method first determines if the object, obj, is the same class as the TrustedClass object and then compares the object's fields to determine if the objects are equivalent.
However, the equals method compares the class names of the object, obj, and the TrustedClass object to determine if they are the same class. As with the previous example using the name of the class to compare the class of objects can lead to the execution of unintended or incorrect code if the object passed to the equals method is of another class with the same name. To compare the class of an object to the intended class, the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.
BadJava
public class TrustedClass { ... @Overridepublic boolean equals(Object obj) { boolean isEquals = false; // first check to see if the object is of the same class if (obj.getClass().getName().equals(this.getClass().getName())) { // then compare object fields ...if (...) {isEquals = true;} } return isEquals; } ... }
In this example, the Java class, TrustedClass, overrides the equals method of the parent class Object to determine equivalence of objects of the class. The overridden equals method first determines if the object, obj, is the same class as the TrustedClass object and then compares the object's fields to determine if the objects are equivalent.
However, the equals method compares the class names of the object, obj, and the TrustedClass object to determine if they are the same class. As with the previous example using the name of the class to compare the class of objects can lead to the execution of unintended or incorrect code if the object passed to the equals method is of another class with the same name. To compare the class of an object to the intended class, the getClass() method and the comparison operator "==" should be used to ensure the correct trusted class is used, as shown in the following example.
GoodJava
public boolean equals(Object obj) { ... // first check to see if the object is of the same class if (obj.getClass() == this.getClass()) {...} ... }