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Cannot Set Static Final Java.lang.string

Updating final or private fields This is a simple trick. This is a second article in the "Forbidden Java actions" series started with Forbidden Java actions: object assignments, type conversions etc on the low level in Java. Look at this code: import java.lang.reflect.Field; public class FinalFieldChange { private static void change(Person p, String name, Object value) throws NoSuchFieldException, IllegalAccessException { Field firstNameField = Person.class.getDeclaredField(name); firstNameField.setAccessible(true); firstNameField.set(p, value); } The reason is that that expression is not a "constant expression" according to the JLS. –Stephen C Sep 27 '13 at 7:53 add a comment| up vote 9 down vote You check over here

final Object base = unsafe.staticFieldBase( fieldToUpdate ); //this is an 'offset' final long offset = unsafe.staticFieldOffset( fieldToUpdate ); //actual update unsafe.putObject( base, offset, 145 ); //ensure the value was updated System.out.println( I got to meet some super people. Compliments? Where does \thepage kick in? http://stackoverflow.com/questions/3301635/change-private-static-final-field-using-java-reflection

This example contains 2 separate classes: SafeKlass defines 2 private static final fields and getters for them; FinalPrivateStaticField class contains update logic. 1 2 3 4 5 6 7 8 9 How difficult is it to practically detect a forgery in a cryptosystem? We are slowly but surely approaching the 100th newsletter edition, which I am hoping to send on the 30th of November, our 4th anniversary of The Java(tm) Specialists' Newsletter.

August 3, 2016 at 11:09 AM Post a Comment Newer Post Older Post Home Subscribe to: Post Comments (Atom) About Me Sebastian Zarnekow I work for itemis at the R&D labs First, we need a class with final fields: public class Person { private final String name; private final int age; private final int iq = 110; private final Object country more hot questions question feed lang-java about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation What now?

Once a person was instantiated, it is not possible to change the value of the field name, is it? By default code using reflection needs particular security permissions. Complaints? http://stackoverflow.com/questions/9391401/java-reflection-change-private-static-final-field-didnt-do-anything Now I know that they evil only in Java.

HTTPS Learn more about clone URLs Download ZIP Code Revisions 1 Stars 1 Java Reflection - Remove "private final" modifiers and set/get value to field Raw MainSandBox.java package sandbox; import java.lang.reflect.Field; When I first saw this, I did not spot the mistake either. When we make bugs like this, the first thing we should do is produce a unit test that shows it. import java.lang.reflect.Field; public class FieldTrouble { public Integer val; public static void main(String...

Do humans have an obligation to prevent animal on animal violence? http://www.javaspecialists.eu/archive/Issue161.html Join them; it only takes a minute: Sign up Change private static final field using Java reflection up vote 296 down vote favorite 121 I have a class with a private setInt(42) for instance would be the same as SecuredClass.securedField = 42;. –Joop Eggen Feb 22 '12 at 8:38 add a comment| 3 Answers 3 active oldest votes up vote 5 down As it was written above, the base object for static fields is their Class object.

We can do the same thing for non-static fields that is, instance variables. Also in this section 8 January 2011 – Enable securitymanager for Spring and Hibernate 10 November 2010 – Implement hash service using JCE 3 Forum posts Modify any Java class field I tried to modify the $VALUES array inside the HumanState enum. Usually, a final field does not have to be synchronized, so what do other threads see if you change its value?

Field.setInt() is invoked to set a field that is of the reference type Integer with a value of primitive type. Documentation The Java™ Tutorials Download Ebooks Download JDK Search Java Tutorials Hide TOC Members Fields Obtaining Field Types Retrieving and Parsing Field Modifiers Getting and Setting Field Values Troubleshooting Methods Obtaining When booking a cruise, how can I find a list of all the fees in advance? My previous approach (newsletter #141) did not work in Java 6.

You can modify final fields, as long as they are non-static. Heinz M. So no.

This hack will allow to change the value of static fields, too.

See also Wikipedia/Bitwise operation share|improve this answer edited Oct 15 '13 at 13:06 bsmk 594516 answered Jul 21 '10 at 16:46 polygenelubricants 215k76444556 115 Extra points for evilness... –thecoop Jul Other names may be trademarks of their respective owners. Pair programming at its best. The readme.txt file has the date 2000/06/02 13:10.

The most disgusting example that I can think of is deliberate chosen with the hope that perhaps people would be instantly disgusted by instead of falling in love with the technique. This hack is more for fun than for serious problem solving. Use Unsafe.putN( base, offset, newValue ) methods for updates. Extreme Java - Advanced Topics.

Use reflection to modify any class/object field. Not the answer you're looking for? The cost of switching to electric cars? The complete code looks like this and as promised, it will print the new name of the person to the console and the changed default name, too.

This all started with an email from Ken Dobson of Edinburgh, which pointed me in the direction of the sun.reflect.ConstructorAccessor, which he claimed could be used to construct enum instances. Typesetting text with math Draw a hollow square of # with given width Is there a word for turning something into a competition? They are not examples which should be followed. –Tom Hawtin - tackline Jul 21 '10 at 19:32 5 well my point ws to find a hack in the between to The reflection package is java.lang.reflect.

September 21, 2013 at 5:41 PM Alin Alx said... Iptables firewall versus nmap and hping3 4. JLS 17.5.3 Subsequent Modification of Final Fields In some cases, such as deserialization, the system will need to change the final fields of an object after construction. The object should not be made visible to other threads, nor should the final fields be read, until all updates to the final fields of the object are complete.

current community chat Stack Overflow Meta Stack Overflow your communities Sign up or log in to customize your list. If AccessibleObject.setAccessible() succeeds, then subsequent operations on this field value will not fail do to this problem. In this newsletter we show how we can do this using the classes in sun.reflect. Then remove ‘final' modifier from this field (you may return it back after update if you wish).

Such updates to static final fields of primitive/String initialized with complile-time expressions will not be visible to clients, because static fields initialized with constant expressions (JLS 15.28) are inlined. JavaSpecialists.eu is not connected to Oracle, Inc. Unfortunately, it is not documented. Usually a Class object will be returned here.