Develop Reference

Save a variable when the server is off

In fact I am making a Minecraft plugin and I was wondering how some plugins (without using DB) manage to keep information even when the server is off.
For example if we make a grade plugin and we create a different list or we stack the players who constitute each. When the server will shut down and restart afterwards, the lists will become empty again (as I initialized them).
So I wanted to know if anyone had any idea how to keep this information.

If a plugin want to save informations only for itself, and it don't need to make it accessible from another way (a PHP website for example), you can use YAML format.
Create the config file :
File usersFile = new File(plugin.getDataFolder(), "user-data.yml");
if(!usersFile.exists()) { // don't exist
usersFile.createNewFile();
// OR you can copy file, but the plugin should contains a default file
/*try (InputStream in = plugin.getResource("user-data.yml");
OutputStream out = new FileOutputStream(usersFile)) {
ByteStreams.copy(in, out);
} catch (Exception e) {
e.printStackTrace();
}*/
}
Load the file as Yaml content :
YamlConfiguration config = YamlConfiguration.loadConfiguration(usersFile);
Edit content :
config.set(playerUUID, myVar);
Save content :
config.save(usersFile);
Also, I suggest you to make I/O async (read & write) with scheduler.
Bonus:
If you want to make ONE config file per user, and with default config, do like that :
File oneUsersFile = new File(plugin.getDataFolder(), playerUUID + ".yml");
if(!oneUsersFile.exists()) { // don't exist
try (InputStream in = plugin.getResource("my-def-file.yml");
OutputStream out = new FileOutputStream(oneUsersFile)) {
ByteStreams.copy(in, out); // copy default to current
} catch (Exception e) {
e.printStackTrace();
}
}
YamlConfiguration userConfig = YamlConfiguration.loadConfiguration(oneUsersFile);
PS: the variable plugin is the instance of your plugin, i.e. the class which extends "JavaPlugin".

You can use PersistentDataContainers:
To read data from a player, use
PersistentDataContainer p = player.getPersistentDataContainer();
int blocksBroken = p.get(new NamespacedKey(plugin, "blocks_broken"), PersistentDataType.INTEGER); // You can also use DOUBLE, STRING, etc.
The Namespaced key refers to the name or pointer to the data being stored. The PersistentDataType refers to the type of data that is being stored, which can be any Java primitive type or String. To write data to a player, use
p.set(new NamespacedKey(plugin, "blocks_broken"), PersistentDataType.INTEGER, blocksBroken + 1);

best way to store data in Java like pickle

Basically, I just want to save two integeres into a File, so that i can reuse them the next time the programm starts. Id like to do it like pickle in python, beacuse writing it just into a txt file is cumbersome. I have read some articles and other questions wehere they say I should use Java serializatio or XML or JSON, but Im not sure wheter that is the right thing in my case. Id like to use the easiest way.
thank you very much in advance for trying to solve my problem! <3

You could use serialization, XML or JSON (usually with additional libraties). An easy way to store configuration data in files is by using Java property files which are supported by the JRE without any additional dependencies. Property files are text files and have a simple key=value syntax, see below. To write two values to a property file you can do
String prop1 = "foo";
String prop2 = "bar";
try (OutputStream output = new FileOutputStream("config.properties")) {
Properties prop = new Properties();
// set the properties value
prop.setProperty("prop1", prop1);
prop.setProperty("prop2", prop2);
// save properties to project root folder
prop.store(output, "my app's config file");
} catch (IOException io) {
io.printStackTrace();
// TODO: improve error handling
}
which should give you something like
#my app's config file
#Sat Feb 29 12:29:27 CET 2020
prop2=bar
prop1=foo
And to load it:
try (InputStream input = new FileInputStream("config.properties")) {
Properties prop = new Properties();
// load a properties file
prop.load(input);
// get the property value and print it out
String prop1 = prop.getProperty("prop1");
String prop2 = prop.getProperty("prop2");
System.out.println("prop1 = " + prop1);
System.out.println("prop2 = " + prop2);
} catch (IOException ex) {
ex.printStackTrace();
// TODO: improve error handling
}
For integer values you would need some type conversion, e.g. the first two lines would be
String prop1 = Integer.toString(23);
String prop2 = Integer.toString(42);
and reading the properties then becomes
int prop1 = Integer.parseInt(prop.getProperty("prop1"));
int prop2 = Integer.parseInt(prop.getProperty("prop2"));
This solution does not scale well in case the number of properties increases or there are frequent changes. For a more generic procedure, see this post: Get int, float, boolean and string from Properties

Chat history forwardedMessages is empty ArrayList

I am trying to implement a java smack client interacting with Openfire server. I have added the plugin for Monitoring service, also enabled archiving. Now I can see the chat history in the openFire Admin Console. I would like to do the same using Smack. This is the code I have written.
XMPPTCPConnection connection = connectToXMPP(Constants.XMPPADMINUSERNAME, Constants.XMPPADMINPWD ,Constants.XMPPDOMAIN);
MamManager mamManager = MamManager.getInstanceFor(connection);
try {
DataForm form = new DataForm(DataForm.Type.submit);
FormField field = new FormField(FormField.FORM_TYPE);
field.setType(FormField.Type.hidden);
field.addValue(MamElements.NAMESPACE);
form.addField(field);
FormField formField = new FormField("with");
formField.addValue("userlocal1#125.99.44.122");
form.addField(formField);
boolean isSupported = mamManager.isSupported();
// "" empty string for before
RSMSet rsmSet = new RSMSet(maxResults, "", RSMSet.PageDirection.before);
MamManager.MamQueryResult mamQueryResult = mamManager.page(form, rsmSet);
// MamManager.MamQueryResult mamQueryResult1 = mamManager.queryArchive(JidCreate.from("userlocal1#125.99.44.122"));
return mamQueryResult;
} catch (Exception e) {
e.printStackTrace();
}
return null;
Now the problem is the forwardedMessages ArrayList is always null. What am I doing wrong?? isSupported is true and I can see the chathistory on admin console… Please guide…

I notice that you're trying to get the last few archived messages, which makes sense. I'm not sure if your 'before' value should be empty though. For testing purposes, try reversing the page direction, and see if you can get the first/oldest few archived messages.

changing log4j file name programatically in osgi maven bundle not working

Im developing a maven-osgi bundle and deploying in karaf.. In that, a piece of code, should get .cfg files from the karaf/etc and im programatically changing them at runtime.. writeTrace() is invoked within 'for loop' from another class. So that I can create different files and corresponding logging should go in to that file.
public void writeLog(int i,String HostName) {
StringBuilder sb = new StringBuilder();
sb.append("\n HEADER : \n");
....
String str = sb.toString();
String logfile = ("/home/Dev/" + HostName + i);
logger = LoggerFactory.getLogger("TracerLog");
updateLog4jConfiguration(logfile);
logger.error(str + i);}
public void updateLog4jConfiguration(String logFile) {
Properties props = new Properties();
try {
// InputStream configStream = getClass().getResourceAsStream(
// "/home/Temp-files/NumberGenerator/src/main/java/log4j.properties");
InputStream configStream = new FileInputStream("etc/org.ops4j.pax.logging.cfg");
props.load(configStream);
System.out.println(configStream);
configStream.close();
} catch (IOException e) {
System.out.println("Error: Cannot laod configuration file ");
}
props.setProperty("log4j.appender.Tracer.File", logFile);
LogManager.resetConfiguration();
PropertyConfigurator.configure(props);
}
and I am able to see new files created with hostname such as (hostname_1 , hostname_2, etc..) but logging happens only at actual appender configured at karaf/etc... thaat is log.txt..
log4j.logger.TracerLog=TRACE,Tracer
log4j.appender.Tracer=org.apache.log4j.RollingFileAppender
log4j.appender.Tracer.MaxBackupIndex=10
log4j.appender.Tracer.MaxFileSize=500KB
log4j.appender.Tracer.File=/home/Dev/log.txt
I got struck in this error.. Dont know whether it has to do something with the karaf or problem with code..???

Why aren't you just using the ConfigurationAdminService for this, instead of altering the file?
Just reference the configuration admin service from the registry and take the configuration with the PID org.ops4j.pax.logging.
With this approach you will have all configuration properties available for your proposal and it is in your code to alter this. It's also possible for you to add new configuration entries. In the end the combination of ConfigurationAdminService and the felix FileInstaller will even persist your changes back to the configuration file.
Btw. did you know that there is a shell command for configuring configurations, so actually also to alter the configuration for the org.ops4j.pax.logging service?
Just do a:
config:list
to retrieve all configurations available
and a
config:list "(service=org.ops4j.pax.logging)"
to retrieve just this information.

Convert embedded pictures in database

I have a 'small' problem. In a database documents contain a richtextfield. The richtextfield contains a profile picture of a certain contact. The problem is that this content is not saved as mime and therefore I can not calculate the url of the image.
I'm using a pojo to retrieve data from the person profile and use this in my xpage control to display its contents. I need to build a convert agent which takes the content of the richtextitem and converts it to mime to be able to calculate the url something like
http://host/database.nsf/($users)/D40FE4181F2B86CCC12579AB0047BD22/Photo/M2?OpenElement
Could someone help me with converting the contents of the richtextitem to mime? When I check for embedded objects in the rt field there are none. When I get the content of the field as stream and save it to a new richtext field using the following code. But the new field is not created somehow.
System.out.println("check if document contains a field with name "+fieldName);
if(!doc.hasItem(fieldName)){
throw new PictureConvertException("Could not locate richtextitem with name"+fieldName);
}
RichTextItem pictureField = (RichTextItem) doc.getFirstItem(fieldName);
System.out.println("Its a richtextfield..");
System.out.println("Copy field to backup field");
if(doc.hasItem("old_"+fieldName)){
doc.removeItem("old_"+fieldName);
}
pictureField.copyItemToDocument(doc, "old_"+fieldName);
// Vector embeddedPictures = pictureField.getEmbeddedObjects();
// System.out.println(doc.hasEmbedded());
// System.out.println("Retrieved embedded objects");
// if(embeddedPictures.isEmpty()){
// throw new PictureConvertException("No embedded objects could be found.");
// }
//
// EmbeddedObject photo = (EmbeddedObject) embeddedPictures.get(0);
System.out.println("Create inputstream");
//s.setConvertMime(false);
InputStream iStream = pictureField.getInputStream();
System.out.println("Create notesstream");
Stream nStream = s.createStream();
nStream.setContents(iStream);
System.out.println("Create mime entity");
MIMEEntity mEntity = doc.createMIMEEntity("PictureTest");
MIMEHeader cdheader = mEntity.createHeader("Content-Disposition");
System.out.println("Set header withfilename picture.gif");
cdheader.setHeaderVal("attachment;filename=picture.gif");
System.out.println("Setcontent type header");
MIMEHeader cidheader = mEntity.createHeader("Content-ID");
cidheader.setHeaderVal("picture.gif");
System.out.println("Set content from stream");
mEntity.setContentFromBytes(nStream, "application/gif", mEntity.ENC_IDENTITY_BINARY);
System.out.println("Save document..");
doc.save();
//s.setConvertMime(true);
System.out.println("Done");
// Clean up if we are done..
//doc.removeItem(fieldName);

Its been a little while now and I didn't go down the route of converting existing data to mime. I could not get it to work and after some more research it seemed to be unnecessary. Because the issue is about displaying images bound to a richtextbox I did some research on how to compute the url for an image and I came up with the following lines of code:
function getImageURL(doc:NotesDocument, strRTItem,strFileType){
if(doc!=null && !"".equals(strRTItem)){
var rtItem = doc.getFirstItem(strRTItem);
if(rtItem!=null){
var personelDB = doc.getParentDatabase();
var dbURL = getDBUrl(personelDB);
var imageURL:java.lang.StringBuffer = new java.lang.StringBuffer(dbURL);
if("file".equals(strFileType)){
var embeddedObjects:java.util.Vector = rtItem.getEmbeddedObjects();
if(!embeddedObjects.isEmpty()){
var file:NotesEmbeddedObject = embeddedObjects.get(0);
imageURL.append("(lookupView)\\");
imageURL.append(doc.getUniversalID());
imageURL.append("\\$File\\");
imageURL.append(file.getName());
imageURL.append("?Open");
}
}else{
imageURL.append(doc.getUniversalID());
imageURL.append("/"+strRTItem+"/");
if(rtItem instanceof lotus.domino.local.RichTextItem){
imageURL.append("0.C4?OpenElement");
}else{
imageURL.append("M2?OpenElement");
}
}
return imageURL.toString()
}
}
}
It will check if a given RT field is present. If this is the case it assumes a few things:
If there are files in the rtfield the first file is the picture to display
else it will create a specified url if the item is of type Rt otherwhise it will assume it is a mime entity and will generate another url.

Not sure if this is an answer but I can't seem to add comments yet. Have you verified that there is something in your stream?
if (stream.getBytes() != 0) {

The issue cannot be resolved "ideally" in Java.
1) if you convert to MIME, you screw up the original Notes rich text. MIME allows only for sad approximation of original content; this might or might not matter.
If it matters, it's possible to convert a copy of the original field to MIME used only for display purposes, or scrape it out using DXL and storing separately - however this approach again means an issue of synchronization every time somebody changes the image in the original RT item.
2) computing URL as per OP code in the accepted self-answer is not possible in general as the constant 0.C4 in this example relates to the offset of the image in binary data of the RT item. Meaning any other design of rich text field, manually entered images, created by different version of Notes - all influence the offset.
3) the url can be computed correctly only by using C API that allows to investigate binary data in rich text item. This cannot be done from Java. IMO (without building JNI bridges etc)