I've written my own 3D Game Engine and started writing a game. I am using OBJ-Models that use the TurboSquid Royalty Free License
Basically, it says that I can use their OBJ-Files but have to implement something that avoids the users to extract the OBJ-Files out of my program.
I've written a converter that extracts the information out of the OBJ-File and creates several float/integer arrays [vertices, vertexCoords, normals, tangents..., indices]
These arrays will be used later for creating the VAOs / VBOs. So my idea was to create a Java class called OBJModelData that contains these arrays. OBJModelDataimplements Serializable. My attempt was to save the class into a file and use them instead of the OBJ-File so that the user cannot see and use the content.
My attempt looks like this:
public void writeToFile(String file){
File f = new File(OBJLoader.RES_LOC+ file +".dat");
try {
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(f));
out.writeObject(this);
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
This results in a file called modelName.dat and looks like this:
Obviously reverse engineering must be done the recreate my arrays. I just do not like the way its written. For example the class that has been serialized is written in the first line. If someone somehow manages the get the source files of my engine by doing some reverse engineering on that he could easily read the file.
Is my method save enough to avoid recreating the obj files and can I still use this method to fulfill the license conditions or is there any other way that is normally used (e.g. in other games/engines) ?
The end of your quote says: "without reverse engineering", so you do not need carry about reverse engineering. You need only "translate" from OBJ to another format of your creation, like you do.
Related
I'm creating a game where all locations of 'blocks' are stored in the variable block_area - an object of class Area. My game has been running correctly for a week now, and I've decided to implement a save and load feature where I save block_area to a file Drifter, with this as my code:
Area block_area; // Later initialized
void saveArea()
{
try
{
FileOutputStream fos = new FileOutputStream(savefile);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(block_area);
oos.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
void loadArea()
{
try
{
FileInputStream fis = new FileInputStream(savefile);
ObjectInputStream ois = new ObjectInputStream(fis);
block_area = (Area)ois.readObject();
ois.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
However, this is my very first time writing and reading an OBJECT to a file, so I don't know much about it. When I try to save the object to the file, it gives me this error:
java.io.NotSerializableException: java.awt.geom.Area
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at Drifter.saveArea(Drifter.java:58)
at Drifter.keyPressed(Drifter.java:315)
...
If anyone can tell me how I can go about writing and reading an object with a file, the help will be greatly appreciated.
TL;DR How do I write the contents of an Area object to a file and read it?
ALSO I have a few follow-up questions:
Is ObjectInputStream the best course of action here? I have seen a few answers where people recommend using XML, and JSON, but I can never find the time to learn about them, and would prefer to stick to a pure Java method (without any third party tools)
Is there any other method of saving an object's information to an external source that I can use instead of file handling?
EDIT - I should also mention that my class implements Serializable
The exception is pretty self explanatory NotSerializableException: java.awt.geom.Area . Any object that you want to serialize must implement the Serializable interface. java,awt.geom.Area does not. Any attributes of that class must also implement Serializable, be a primitive, or be defined as transient.
I'd suggest either Figuring out a way to read Area into an object that does implement Serializable. When you read it back out, you can construct a new Area object. This is probably what the JSON/XML method mentioned in the comments is doing. The added benefit of a human readable storage format is that you can edit it in a text editor. You won't be able to do that with the binary output of a serialized object`.
So I'm in the process of developing a Java IRC bot as a bit of a side project for a friend of mine, and while development is going well, I'm a little unsure as how to save the current state of certain variables in between sessions. It doesn't have a GUI, so I didn't think that it would be too complex, but my searching efforts have been futile thus far.
Thanks.
It will depend on the sort of variables you want to keep, but all methods will require you to write some sort data to a file.
If you only need to keep a handful of variables, you could consider implementing a .config file that could be a simple delimited text file.
If it's an entire object that you want to keep track of, say, a player in an irc game, one option you have is to parse the object into JSON, and save it to a textfile, for reading later. You can use Gson for this
example for a 'player' object:
public String savePlayer(String playerName){
Gson gsonPretty = new GsonBuilder().setPrettyPrinting().create();
String playerFile = System.getProperty("user.dir")+"\\players\\"+playerName;
String jsonplayers = gsonPretty.toJson(players.get(playerName));
try{
FileWriter writer = new FileWriter(playerFile+".json");
writer.write(jsonplayers);
writer.close();
return "Player file saved successfully!";
}catch(Exception e){
e.printStackTrace();
}
return "Something went wrong";
}
you can then create a load method that either has the file name hard coded, or a string input to determine which file to load, and use something like:
playerFromJson = gson.fromJson(jsonString, Player.class);
to use that object in the code
I am a newbie programmer, very newbie..
I am trying to write a program to test our website and am using Java and Selenium.
The issue is I want to create a "table" or a "reference" that will allow me to store variables that can easily be called back and used in different calls.
I tried to use a HashMap but found it was no good because when I rerun my testing code there is a new hashmap each time. I want something that can store the values and remember them the next time I run the code.
I looked at creating a mysql table but I can't figure out how to recall the variables out of the table once they have been created.
I hope this makes some sense. :0) Pls check out below if an example would be more useful
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Here is an example of the hashmap that I was using:
HashMap idTable = new HashMap();
idTable.put("GroupName", new String("Group " +
Long.toHexString(Double.doubleToLongBits(Math.random()))));
element = driver.findElement(By.id("name"));
element.sendKeys((String)idTable.get("GroupName"));
FYI: The reason this doesn't work for me is that I want to be able to wrap it in an "if" statement; to tell the computer that if the variable called "GroupName" already exists then don't do it again.. however every time I run the script I make a call to the function [HashMap idTable = new HashMap();] and I don't know how to NOT make that call because the HashMap isn't saved anywhere.. it is created new each time.
Thanks,
Orli
not sure where to add this: but following the first suggestion here is what I did.
HashMap idTable;
try{
ObjectInputStream is = new ObjectInputStream(
new FileInputStream("C:\Documents and Settings\My Documents\Selenium local\hashmap.dat"));
idTable = (HashMap) is.readObject();
}
catch(Exception e){
idTable = new HashMap();
}
AND then:
try{
ObjectOutputStream os = new ObjectOutputStream (
new FileOutputStream("C:\Documents and Settings\My Documents\Selenium local\hashmap.dat"));
os.writeObject(idTable);
os.close();
}
catch (Exception e){
}
It works. :0) Thanks for the help!
Use an instance of Properties for simple string key/value pairs. It is a Map, like HashMap but has load and store methods for reading/writing its contents to a file. This should be more than adequate for simple testing usage.
It is commonly used for loading configuration files.
You must store them somewhere not in the code, as the code goes bye-bye whenever the JVM shuts down. Two good options to do this are
Using SQL database, research this more via google if you want
Via files, simply writing your HashMap database to a file at the end of your program (Do Runtime.addShutdownHook, and pass it a thread whcih stores your hashmap to the file), and have it read from the file at the begining of the code (if the file is nonexistant, make a new one, and store an empty hashmap to it)
I recently found out about java.util.Properties, which allows me to write and read from a config without writing my own function for it.
I was excited since it is so easy to use, but later noticed a flaw when I stored the modified config file.
Here is my code, quite simple for now:
FileWriter writer = null;
Properties configFile = new Properties();
configFile.load(ReadFileTest.class.getClassLoader().getResourceAsStream("config.txt"));
String screenwidth = configFile.getProperty("screenwidth");
String screenheight = configFile.getProperty("screenheight");
System.out.println(screenwidth);
System.out.println(screenheight);
configFile.setProperty("screenwidth", "1024");
configFile.setProperty("screenheight", "600");
try {
writer = new FileWriter("config.txt" );
configFile.store(writer, null);
} catch (IOException e) {
e.printStackTrace();
}
writer.flush();
writer.close();
The problem I noticed was that the config file I try to edit is stored like this:
foo: bar
bar: foo
foobar: barfoo
However, the output after properties.store(writer, null) is this:
foo=bar
bar=foo
foobar=barfoo
The config file I edit is not for my program, it is for an other application that needs the config file to be in the format shown above with : as divider or else it will reset the configuration to default.
Does anybody know how to easily change this?
I searched through the first 5 Google pages now but found noone with a similar problem.
I also checked the Javadoc and found no function that allows me to change it without writing a class for myself.
I would like to use Properties for now since it is there and quite easy to use.
I also got the idea of just replacing all = with : after I saved the file but maybe someone got a better suggestion?
Don't use a tool that isn't designed for the task - don't use Properties here. Instead, I'd just write your own - should be easy enough.
You can still use a Properties instance as your "store", but don't use it for serializing the properties to text. Instead, just use a FileWriter, iterate through the properties, and write the lines yourself - as key + ": " + value.
New idea here
Your comment about converting the = to : got me thinking: Properties.store() writes to a Stream. You could use an in-memory ByteArrayOutputStream, convert as appropriate in memory before you write to a file, then write the file. Likewise for Properties.load(). Or you could insert FilterXXXs instead. (I'd probably do it in memory).
I was looking into how hard it would be to subclass. It's nearly impossible. :-(
If you look at the source code for Properties, (I'm looking at Java 6) store() calls store0(). Now, unfortunately, store0 is private, not protected, and the "=" is given as a magic constant, not something read from a property. And it calls another private method called saveConvert() that also has a lot of magic constants.
Overall, I rate this code as D- quality. It breaks almost all the rules of good code and good style.
But, it's open source, so, theoretically, you could copy and paste (and improve!) a bunch of code into your own BetterProperties class.
I have a file that contains bytes, chars, and an object, all of which need to be written then read. What would be the best way to utilize Java's different IO streams for writing and reading these data types? More specifically, is there a proper way to add delimiters and recognize those delimiters, then triggering what stream should be used? I believe I need some clarification on using multiple streams in the same file, something I have never studied before. A thorough explanation would be a sufficient answer. Thanks!
As EJP already suggested, use ObjectOutputStream and ObjectInputStream an0d wrap your other elements as an object(s). I'm giving as an answer so I could show an example (it's hard to do it in comment) EJP - if you want to embed it in your question, please do and I'll delete the answer.
class MyWrapedData implements serializeable{
private String string1;
private String string2;
private char char1;
// constructors
// getters setters
}
Write to file:
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(fileName));
out.writeObject(myWrappedDataInstance);
out.flush();
Read from file
ObjectInputStream in = new ObjectInputStream(new FileInputStream(fileName));
Object obj = in.readObject();
MyWrapedData wraped = null;
if ((obj != null) && (obj instanceof MyWrappedData))
wraped = (MyWrapedData)obj;
// get the specific elements from the wraped object
see very clear example here: Read and Write
Redesign the file. There is no sensible way of implementing it as presently designed. For example the object presupposes an ObjectOutputStream, which has a header - where's that going to go? And how are you going to know where to switch from bytes to chars?
I would probably use an ObjectOutputStream for the whole thing and write everything as objects. Then Serialization solves all those problems for you. After all you don't actually care what's in the file, only how to read and write it.
Can you change the structure of the file? It is unclear because the first sentence of your question contradicts being able to add delineators. If you can change the file structure you could output the different data types into separate files. I would consider this the 'proper' way to delineate the data streams.
If you are stuck with the file the way it is then you will need to write an interface to the file's structure which in practice is a shopping list of read operations and a lot of exception handling. A hackish way to program because it will require a hex editor and a lot of trial and error but it works in certain cases.
Why not write the file as XML, possibly with a nice simple library like XSTream. If you are concerned about space, wrap it in gzip compression.
If you have control over the file format, and it's not an exceptionally large file (i.e. < 1 GiB), have you thought about using Google's Protocol Buffers?
They generate code that parses (and serializes) file/byte[] content. Protocol buffers use a tagging approach on every value that includes (1) field number and (2) a type, so they have nice properties such as forward/backward compatability with optional fields etc. They are fairly well optimized for both speed and file size, adding only ~2 bytes of overhead for a short byte[], with ~2-4 additional bytes to encode the length on larger byte[] fields (VarInt encoded lengths).
This could be overkill, but if you have a bunch of different fields & types, protobuf is really helpful. See: http://code.google.com/p/protobuf/.
An alternative is Thrift by Facebook, with support for a few more languages although possibly less use in the wild last I checked.
If the structure of your file is not fixed, consider using a wrapper per type. First you need to create the interface of your wrapper classes….
interface MyWrapper extends Serializable {
void accept(MyWrapperVisitor visitor);
}
Then you create the MyWrapperVisitor interface…
interface MyWrapperVisitor {
void visit(MyString wrapper);
void visit(MyChar wrapper);
void visit(MyLong wrapper);
void visit(MyCustomObject wrapper);
}
Then you create your wrapper classes…
class MyString implements MyWrapper {
public final String value;
public MyString(String value) {
super();
this.value = value;
}
#Override
public void accept(MyWrapperVisitor visitor) {
visitor.visit(this);
}
}
.
.
.
And finally you read your objects…
final InputStream in = new FileInputStream(myfile);
final ObjectInputStream objIn = new ObjectInputStream(in);
final MyWrapperVisitor visitor = new MyWrapperVisitor() {
#Override
public void visit(MyString wrapper) {
//your logic here
}
.
.
.
};
//loop over all your objects here
final MyWrapper wrapper = (MyWrapper) objIn.readObject();
wrapper.accept(visitor);