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);

How to limit size of velocity output

I am using java and Apache Velocity 1.7 to evaluate template
Following is sample code:
public void internalEvaluate(Map<String, Object> customContext, String templateText) throws IOException {
// add custom context to VelocityContext
VelocityContext context = new VelocityContext();
for (Map.Entry<String, Object> entry : customContext.entrySet()) {
context.put(entry.getKey(), entry.getValue());
}
// define writer
StringWriter output = new StringWriter();
// define logTag
String logTag = "TestVTL";
// check input template text
if (templateText == null)
templateText = "$noDescription";
Velocity.evaluate(context, output, logTag, templateText);
// write output to file
saveToFile(out);
}
However, specific customContext or templateText may make a large output.
The output can be created as file but cannot be opened by editor.
Below are my questions
Q1.
I would like to limit or check size of output at runtime (or before calling evaluate()) and throw warning message about creating too large file.
Does Velocity provide configure or Api to do something like this?
Q2.
Evaluation process may take a long time.
I would like to know progress status in velocity evaluation process.
Is it possible to get progress information?
Best regards,

Since Velocity only sees a Writer class, it has no mean of counting the output size.
Your best option would be to implement a CustomStringWriter class that will throw an exception when its internal size has reached a certain limit.

Spring Batch creating multiple files .Gradle based project

I need to create 3 separate files.
My Batch job should read from Mongo then parse through the information and find the "business" column (3 types of business: RETAIL,HPP,SAX) then create a file for their respective business. the file should create either RETAIL +formattedDate; HPP + formattedDate; SAX +formattedDate as the file name and the information found in the DB inside a txt file. Also, I need to set the .resource(new FileSystemResource("C:\filewriter\index.txt)) into something that will send the information to the right location, right now hard coding works but only creates one .txt file.
example:
#Bean
public FlatFileItemWriter<PaymentAudit> writer() {
LOG.debug("Mongo-writer");
FlatFileItemWriter<PaymentAudit> flatFile = new
FlatFileItemWriterBuilder<PaymentAudit>()
.name("flatFileItemWriter")
.resource(new FileSystemResource("C:\\filewriter\\index.txt))
//trying to create a path instead of hard coding it
.lineAggregator(createPaymentPortalLineAggregator())
.build();
String exportFileHeader =
"CREATE_DTTM";
StringHeaderWriter headerWriter = new
StringHeaderWriter(exportFileHeader);
flatFile.setHeaderCallback(headerWriter);
return flatFile;
}
My idea would be something like but not sure where to go:
public Map<String, List<PaymentAudit>> getPaymentPortalRecords() {
List<PaymentAudit> recentlyCreated =
PaymentPortalRepository.findByCreateDttmBetween(yesterdayMidnight,
yesterdayEndOfDay);
List<PaymentAudit> retailList = new ArrayList<>();
List<PaymentAudit> saxList = new ArrayList<>();
List<PaymentAudit> hppList = new ArrayList<>();
//String exportFilePath = "C://filewriter/";??????
recentlyCreated.parallelStream().forEach(paymentAudit -> {
if (paymentAudit.getBusiness().equalsIgnoreCase(RETAIL)) {
retailList.add(paymentAudit);
} else if
(paymentAudit.getBusiness().equalsIgnoreCase(SAX)) {
saxList.add(paymentAudit);
} else if
(paymentAudit.getBusiness().equalsIgnoreCase(HPP)) {
hppList.add(paymentAudit);
}
});

To create a file for each business object type, you can use the ClassifierCompositeItemWriter. In your case, you can create a writer for each type and add them as delegates in the composite item writer.
As per creating the filename dynamically, you need to use a step scoped writer. There is an example in the Step Scope section of the reference documentation.
Hope this helps.

scriptella executor with xml as string instead of file

I am trying to use scriptella in my project to copy data from one db to another, now the application has a frontend which users can use to create mapping between tables and create dynamic queries, now currently once the user submits the frontend queries are passed via a query engine and a scriptella xml is created using freemarker template
however to execute the xml the executor expects a file instead of a xml string currently i am achieving this by creating a xml in temp directory and deleting it post execution of query, is there any way i can skip file creation and execute the query as a xml string

You can create a custom URLStreamHandler that will serve streams directly from memory. This is similar to what was done in AbstractTestCase. It can be registered by calling URL.setURLStreamHandlerFactory. See Registering and using a custom java.net.URL protocol or Is it possible to create an URL pointing to an in-memory object?
After that, use
EtlExecutor.newExecutor(java.net.URL) with the new URI, e.g. new URL("memory://file")

I had a similar use case. I downloaded the code and made a small change in the core. Due to some private functions I had no choice.
in
package scriptella.configuration.ConfigurationFactory
I added the following function:
public ConfigurationEl createConfigurationFromTxt(String xml, final ParametersCallback externalParameters ) {
try {
DocumentBuilder db = DBF.newDocumentBuilder();
db.setEntityResolver(ETL_ENTITY_RESOLVER);
db.setErrorHandler(ETL_ERROR_HANDLER);
final InputStream in = new ByteArrayInputStream(xml.getBytes());
final Document document = db.parse(in);
HierarchicalParametersCallback params = new HierarchicalParametersCallback(
externalParameters == null ? NullParametersCallback.INSTANCE : externalParameters, null);
PropertiesSubstitutor ps = new PropertiesSubstitutor(params);
return new ConfigurationEl(new XmlElement(
document.getDocumentElement(), resourceURL, ps), params);
} catch (IOException e) {
throw new ConfigurationException("Unable to load document: " + e, e);
} catch (Exception e) {
throw new ConfigurationException("Unable to parse document: " + e, e);
}
}
Then from my code I can do something like this:
ConfigurationFactory cf = new ConfigurationFactory();
ConfigurationEl conf = cf.createConfigurationFromTxt(FETCH_ETLS, p);
EtlExecutor exec = new EtlExecutor(conf);

How to edit MS Word documents using Java?

I do have few Word templates, and my requirement is to replace some of the words/place holders in the document based on the user input, using Java. I tried lot of libraries including 2-3 versions of docx4j but nothing work well, they all just didn't do anything!
I know this question has been asked before, but I tried all options I know. So, using what java library I can "really" replace/edit these templates? My preference goes to the "easy to use / Few line of codes" type libraries.
I am using Java 8 and my MS Word templates are in MS Word 2007.
Update
This code is written by using the code sample provided by SO member Joop Eggen
public Main() throws URISyntaxException, IOException, ParserConfigurationException, SAXException
{
URI docxUri = new URI("C:/Users/Yohan/Desktop/yohan.docx");
Map<String, String> zipProperties = new HashMap<>();
zipProperties.put("encoding", "UTF-8");
FileSystem zipFS = FileSystems.newFileSystem(docxUri, zipProperties);
Path documentXmlPath = zipFS.getPath("/word/document.xml");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(Files.newInputStream(documentXmlPath));
byte[] content = Files.readAllBytes(documentXmlPath);
String xml = new String(content, StandardCharsets.UTF_8);
//xml = xml.replace("#DATE#", "2014-09-24");
xml = xml.replace("#NAME#", StringEscapeUtils.escapeXml("Sniper"));
content = xml.getBytes(StandardCharsets.UTF_8);
Files.write(documentXmlPath, content);
}
However this returns the below error
java.nio.file.ProviderNotFoundException: Provider "C" Not found
at: java.nio.file.FileSystems.newFileSystem(FileSystems.java:341) at java.nio.file.FileSystems.newFileSystem(FileSystems.java:341)
at java.nio.fileFileSystems.newFileSystem(FileSystems.java:276)

One may use for docx (a zip with XML and other files) a java zip file system and XML or text processing.
URI docxUri = ,,, // "jar:file:/C:/... .docx"
Map<String, String> zipProperties = new HashMap<>();
zipProperties.put("encoding", "UTF-8");
try (FileSystem zipFS = FileSystems.newFileSystem(docxUri, zipProperties)) {
Path documentXmlPath = zipFS.getPath("/word/document.xml");
When using XML:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(Files.newInputStream(documentXmlPath));
//Element root = doc.getDocumentElement();
You can then use XPath to find the places, and write the XML back again.
It even might be that you do not need XML but could replace place holders:
byte[] content = Files.readAllBytes(documentXmlPath);
String xml = new String(content, StandardCharsets.UTF_8);
xml = xml.replace("#DATE#", "2014-09-24");
xml = xml.replace("#NAME#", StringEscapeUtils.escapeXml("Sniper")));
...
content = xml.getBytes(StandardCharsets.UTF_8);
Files.delete(documentXmlPath);
Files.write(documentXmlPath, content);
For a fast development, rename a copy of the .docx to a name with the .zip file extension, and inspect the files.
File.write should already apply StandardOpenOption.TRUNCATE_EXISTING, but I have added Files.delete as some error occured. See comments.

Try Apache POI. POI can work with doc and docx, but docx is more documented therefore support of it better.
UPD: You can use XDocReport, which use POI. Also I recomend to use xlsx for templates because it more suitable and more documented

I have spent a few days on this issue, until I found that what makes the difference is the try-with-resources on the FileSystem instance, appearing in Joop Eggen's snippet but not in question snippet:
try (FileSystem zipFS = FileSystems.newFileSystem(docxUri, zipProperties))
Without such try-with-resources block, the FileSystem resource will not be closed (as explained in Java tutorial), and the word document not modified.

Stepping back a bit, there are about 4 different approaches for editing words/placeholders:
MERGEFIELD or DOCPROPERTY fields (if you are having problems with this in docx4j, then you have probably not set up your input docx correctly)
content control databinding
variable replacement on the document surface (either at the DOM/SAX level, or using a library)
do stuff as XHTML, then import that
Before choosing one, you should decide whether you also need to be able to handle:
repeating data (eg adding table rows)
conditional content (eg entire paragraphs which will either be present or absent)
adding images
If you need these, then MERGEFIELD or DOCPROPERTY fields are probably out (though you can also use IF fields, if you can find a library which supports them). And adding images makes DOM/SAX manipulation as advocated in one of the other answers, messier and error prone.
The other things to consider are:
your authors: how technical are they? What does that imply for the authoring UI?
the "user input" you mention for variable replacement, is this given, or is obtaining it part of the problem you are solving?

Please try this to edit or replace the word in document
public class UpdateDocument {
public static void main(String[] args) throws IOException {
UpdateDocument obj = new UpdateDocument();
obj.updateDocument(
"c:\\test\\template.docx",
"c:\\test\\output.docx",
"Piyush");
}
private void updateDocument(String input, String output, String name)
throws IOException {
try (XWPFDocument doc = new XWPFDocument(
Files.newInputStream(Paths.get(input)))
) {
List<XWPFParagraph> xwpfParagraphList = doc.getParagraphs();
//Iterate over paragraph list and check for the replaceable text in each paragraph
for (XWPFParagraph xwpfParagraph : xwpfParagraphList) {
for (XWPFRun xwpfRun : xwpfParagraph.getRuns()) {
String docText = xwpfRun.getText(0);
//replacement and setting position
docText = docText.replace("${name}", name);
xwpfRun.setText(docText, 0);
}
}
// save the docs
try (FileOutputStream out = new FileOutputStream(output)) {
doc.write(out);
}
}
}
}