The need:
I want to write data into compressed and normal format as well. When I'll have to write data into compressed format "useCompression" will be sent as "true" and "useCompression" will be false when data needs to be stored in normal(as it is given to the Writer class) format.
The problem here is, how will I identify whether the data is compressed or not later when Reader class is trying to read the data?
So, to solve the problem, I am writing "1" into file if is "useCompression" is true and "0" if "useCompression" is false.
writing is fine, but when we try to skip the first element using "fIn.skip(1)" cause it is the identifier and not actual data, it is leaving behind some garbage value.
For, example, I am trying to write "2019-07-31" into a file and "useCompression" is false, so my file will hold "02019-07-31" and post "fIn.skip(1)" call it should hold "2019-07-31" but it is holding "^#2019-07-31".
Please help me figure out what I am doing wrong here
I've tried to update Reader class's constructor as:
public Reader(String key)
{
mKey = key;
try {
FileInputStream fIn = new FileInputStream(streamFileForKey(key));
byte[] firstByte = new byte[1];
int read = fIn.read(firstByte);
boolean shouldUseDecompression = (1 == firstByte[0]);
if (shouldUseDecompression) {
mFin = new GZIPInputStream(fIn);
}
else {
mFin = fIn;
}
}
catch (Exception e) {
System.out.println("Failed to open (r) key " + key + " exception : " + e);
}
}
But it does not solve the problem.
The actual code is:
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.DataOutputStream;
import java.util.zip.GZIPOutputStream;
import java.util.zip.GZIPInputStream;
public class forStackOverflow {
public static void main(String []args) {
// Write to normal file
mReader1 = new Reader(mInputFileName);
mWriter1 = new Writer(mOutputFilename1, false);
int availableBytes = mReader1.availableBytes();
int readBytes = 1000;
while (availableBytes > 0)
{
if (availableBytes >= 1000) {
availableBytes = availableBytes - readBytes;
}
else {
readBytes = availableBytes;
availableBytes = availableBytes - readBytes;
}
mWriter1.write(mReader1.read(readBytes), 0, readBytes);
}
mReader1.close();
mWriter1.close();
}
private static File streamFileForKey(String key)
{
return new File(key);
}
static String mInputFileName = "~/Downloads/inputStream.txt";
static String mOutputFilename1 = "~/Downloads/outputStream.txt";
static Reader mReader1;
static Writer mWriter1;
private static class Writer
{
public Writer(String key, boolean useCompression) {
mKey = key;
try {
FileOutputStream fileOutput = new FileOutputStream(streamFileForKey(key));
if (useCompression) {
fileOutput.write(1);
gOutputStream = new GZIPOutputStream(fileOutput);
}
else {
fileOutput.write(0);
gOutputStream = new DataOutputStream(fileOutput);
}
}
catch (Exception e) {
System.out.println("Got error while opening stream for " + mKey + ". Ex: " + e);
}
}
public boolean write(byte[] bytes, int pos, int len)
{
boolean retVal = true;
if (gOutputStream == null) {
return false;
}
try {
gOutputStream.write(bytes, pos, len);
retVal = true;
}
catch (Exception e) {
System.out.println("Failed to write " + len + " bytes to key " +
mKey + e);
retVal = false;
}
return retVal;
}
public void close()
{
if (gOutputStream != null) {
try {
gOutputStream.close();
}
catch (Exception e) {
System.out.println("Failed to close key " + mKey + e);
}
gOutputStream = null;
}
}
private String mKey;
private OutputStream gOutputStream;
}
private static class Reader
{
public Reader(String key)
{
mKey = key;
try {
FileInputStream fIn = new FileInputStream(streamFileForKey(key));
if (shouldUseDecompression()) {
long skipped = fIn.skip(1);
mFin = new GZIPInputStream(fIn);
}
else {
long skipped = fIn.skip(1);
mFin = fIn;
}
}
catch (Exception e) {
System.out.println("Failed to open (r) key " + key + " exception : " + e);
}
}
public byte[] read(int len)
{
if (mFin == null) {
return null;
}
byte[] b = null;
try {
b = new byte[len];
int read;
read = mFin.read(b, 0, len);
if (read <= 0) {
return null;
}
}
catch (Exception e) {
System.out.println("Failed to read " + len + " bytes from key " +
mKey + " exception : " + e);
}
return b;
}
public void close()
{
if (mFin != null) {
try {
mFin.close();
}
catch (Exception e) {
System.out.println("Failed to close key " + mKey + " exception : " + e);
}
mFin = null;
}
}
private boolean shouldUseDecompression()
{
boolean retVal = false;
try {
FileInputStream fIn = new FileInputStream(streamFileForKey(mKey));
byte[] firstByte = new byte[1];
int read = fIn.read(firstByte);
// If first byte is `1` the we need to use decompression on it.
retVal = (1 == firstByte[0]);
fIn.close();
}
catch(Exception e) {
System.out.println("Exception in shouldUseDecompression() : " + e);
retVal = false;
}
return retVal;
}
public int availableBytes()
{
int available = 0;
try {
if (mFin != null) {
available = mFin.available();
}
}
catch (IOException e) {
System.out.println("Failed to read available bytes for " + mKey + ". Exception : " + e);
}
return available;
}
private String mKey;
private InputStream mFin;
}
}
The expected result should be, post "fIn.skip(1)" call file should hold "2019-07-31" and not "^#2019-07-31".
After a lot of struggle, I found out that it was the expected result.
^# was nothing but the binary 0 I was writing from Writer class's constructor incase useCompression was false.
From line fileOutput.write(0);.
Today I meet a problem with "java" command.
I work in Intellij IDEA and think that I wrong classpath to "java" command.
Please, help me.
package ru.mch;
import ru.mch.RunTask;
public class Program {
public static void main(String[] args) {
String taskCode = "class UserProgram{ public static void main(String[] args) { int b = 3 + 1; System.out.println(b);}}";
String packageName = "package ru.mch; ";
String all = packageName + taskCode ;
RunTask runTask = new RunTask(all);
int result = runTask.run();
}
}
I want to get program code from String, create new java class, write code to the class and compile and run new java class.
package ru.mch;
import java.io.*;
public class RunTask {
private String answerFromPage;
private int programExitValue;
public RunTask(String answerFromPage) {
this.answerFromPage = answerFromPage;
this.programExitValue = 0;
}
private static void printLines(String name, InputStream ins) throws Exception {
String line = null;
BufferedReader in = new BufferedReader(
new InputStreamReader(ins));
while ((line = in.readLine()) != null) {
System.out.println(line);
}
}
private static int runProcess(String command) throws Exception {
Process pro = Runtime.getRuntime().exec(command);
printLines(/*command + */" stdout:", pro.getInputStream());
printLines(" stderr:", pro.getErrorStream());
pro.waitFor();
System.out.println(command + " exit value = " + pro.exitValue());
return pro.exitValue();
}
public int run(){
//String fileName = "src\\main\\java\\ru\\mch\\UserProgram.java";
String fileName = "src\\main\\java\\ru\\mch\\UserProgram.java";
File f = new File(fileName);
f.getParentFile().mkdirs();
try {
f.createNewFile();
} catch (IOException e) {
throw new IllegalArgumentException("File creating error");
}
try(FileWriter writer = new FileWriter(fileName, false))
{
writer.write(this.answerFromPage);
writer.flush();
}
catch(IOException ex){
System.out.println(ex.getMessage());
}
try {
System.out.println(runProcess("javac -sourcepath src src\\main\\java\\ru\\mch\\UserProgram.java"));
System.out.println("------------");
this.programExitValue = runProcess("java src\\main\\java\\ru.mch.UserProgram");
} catch (Exception e) {
e.printStackTrace();
}
return this.programExitValue;
}
}
This is IDEA log :
javac src\main\java\ru\mch\UserProgram.java exit value = 0
0
------------
Error: Could not find or load main class src\main\java\ru.mch.UserProgram
java src\main\java\ru.mch.UserProgram exit value = 1
New class was created and .class too.
I try to write full classpath, try to write '\' instead of '.' in package name, but all is wrong.
Sorry for my bad English.
Use the following command:
java -cp src\main\java ru.mch.UserProgram
I have written a small program in Java (eclipse) to run R using JRI (rjava). All paths are set. The problem is that while I can run numeric functions (like add), I can't run a string function like cat. (please excuse any errors; I did Java coding for the first time yesterday).
package com.trial.ss;
import org.rosuda.JRI.Rengine;
public class RScriptConnection {
public Rengine getRScriptEngine() throws Exception {
Rengine engine = null;
try {
engine = Rengine.getMainEngine();
if (engine == null) engine = new Rengine(new String[] {
"--vanilla"
},
false, null);
/* if (!engine.waitForR()) {
System.out.println("Unable to load R");
return null;
} else*/
System.out.println("Connected to R");
String rScriptSourceFile = "source('" + RScriptConstant.RS_FILE_LOCATION + "',verbose=TRUE)";
engine.eval(rScriptSourceFile);
System.out.println("loading RScript file || completed");
//return engine;
} catch(Exception ex) {
System.out.println("Exeption while connecting to REngine " + ex.getMessage());
//throw new Exception("Error while creating REngine in RScriptConnection:getRScriptEngine()");
}
return engine;
}
public static void main(String[] args) {
String libpath = System.getProperty("java.library.path");
System.out.println("##############libpath=" + libpath);
// System.out.println("Method to be called in RScript=" + "Add(x1 = " + 10 + ", x2 = " + 20 + ", x3 = " + 30 + ", x4 = " + 50 + ")");
RScriptConnection rScriptConnection = new RScriptConnection();
try {
Rengine rEngine = rScriptConnection.getRScriptEngine();
String Value1 = "\"Advisory\"";
String Value2 = "\"Assurance\"";
double svalue = rEngine.eval("(1+2)").asDouble();
System.out.println("mvalue=" + svalue);
System.out.println("method to be called in RScript is " + "cat(" + Value1 + "," + Value2 + ")");
String value = rEngine.eval("cat(" + Value1 + "," + Value2 + ")").asString();
System.out.println(value);
rEngine.end();
} catch(Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Please help me understand why my string function like cat doesn't work.
Here is the output I am currently getting:
##############libpath=C:\Users\myname\Documents\R\win-library\3.3\rJava\jri\x64
Connected to R
loading RScript file || completed
mvalue=3.0
method to be called in RScript is cat("Advisory","Assurance")
null
Why am I getting null in the end? I should get Advisory Assurance
Bellow is an example of how to show R output into Java. You basically have to implement RMainLoopCallbacks.
import org.rosuda.JRI.RMainLoopCallbacks;
import org.rosuda.JRI.Rengine;
import java.util.logging.Logger;
public class Runner {
private static Logger log = Logger.getLogger("Runner");
static class LoggingConsole implements RMainLoopCallbacks {
private Logger log;
LoggingConsole(Logger log) {
this.log = log;
}
public void rWriteConsole(Rengine re, String text, int oType) {
log.info(String.format("rWriteConsole: %s", text));
}
public void rBusy(Rengine re, int which) {
log.info(String.format("rBusy: %s", which));
}
public void rShowMessage(Rengine re, String message) {
log.info(String.format("rShowMessage: %s", message));
}
public String rReadConsole(Rengine re, String prompt, int addToHistory) {
return null;
}
public String rChooseFile(Rengine re, int newFile) {
return null;
}
public void rFlushConsole(Rengine re) {
}
public void rLoadHistory(Rengine re, String filename) {
}
public void rSaveHistory(Rengine re, String filename) {
}
}
Rengine engine = new Rengine(new String[] {"--no-save"}, false, new LoggingConsole(log));
...
// Use the engine somewhere to evaluate a R method and see the output
engine.eval(rScriptSourceFile);
}
I was able to create a backup of my current mysql database as .SQL file using the mysqldump.exe with the help of the following java code.
Process runProcess = Runtime.getRuntime().exec("C:\\SCM Files\\SQL Backup\\mysqldump.exe -uroot -p123 rr -r\"C:\\SCM Files\\SQL Backup\\RR.sql");
Now I want to restore this same .SQL Backup file to mysql database using java code similar to above on the event of a button clicked.
Thanks a lot :)
So now I tried this ;
Process runProcess = Runtime.getRuntime().exec("C:\\SCM Files\\SQL Backup\\mysqldump.exe -uroot -p123 rr < C:\\SCM Files\\SQL Backup\\RR.sql");
Still it didn't work :/
public static boolean restoreDB(String dbName, String dbUserName, String dbPassword, String source) {
String[] executeCmd = new String[]{"mysql", "--user=" + dbUserName, "--password=" + dbPassword, dbName,"-e", " source "+source};
Process runtimeProcess;
try {
runtimeProcess = Runtime.getRuntime().exec(executeCmd);
int processComplete = runtimeProcess.waitFor();
if (processComplete == 0) {
System.out.println("Backup restored successfully");
return true;
}
} else {
System.out.println("Could not restore the backup");
}
} catch (Exception ex) {
ex.printStackTrace();
}
return false;
}
source example : "E:\\My Backup\\Test\\file.sql"
Runtime.getRuntime().exec("mysql -u username -ppassword database_name FILE.sql")
This statement will regenerate database from the file
You have to use java swings where you can design forms. Here is some code which can do that.
import javax.swing.JFrame;
public final class RestoreMySQLDatabase extends JFrame {
private static final long serialVersionUID = 1L;
public static void main(String[] args) {
RestoreMySQLDatabase restoreMySQL = new RestoreMySQLDatabase();
restoreMySQL.setTitle("Restore mysql database");
javax.swing.JButton butRestore = new javax.swing.JButton("Restore");
butRestore.addActionListener(new java.awt.event.ActionListener(){
public void actionPerformed(java.awt.event.ActionEvent event){
try{
Runtime.getRuntime().exec("C:\\SCM Files\\SQL Backup\\mysqldump.exe -uroot -p123 rr -r\"C:\\SCM Files\\SQL Backup\\RR.sql");
javax.swing.JOptionPane.showMessageDialog((javax.swing.JButton)event.getSource(), "Successfully restored");
}catch(java.lang.Exception e){
javax.swing.JOptionPane.showMessageDialog((javax.swing.JButton)event.getSource(), "Not able to restore");
}
}
});
}
}
I tried this code and works as perfect!
String[] restoreCmd = new String[]{"mysql ", "--user=" + DB.DB_USERNAME, "--password=" + DB.DB_PASSWORD, "-e", "source " + pathToFile};
try {
Process runtimeProcess = Runtime.getRuntime().exec(restoreCmd);
int processComplete = runtimeProcess.waitFor();
if (processComplete == 0) {
System.out.println("Done");
} else {
System.out.println("Failed");
}
} catch (Exception ex) {
ex.printStackTrace();
}
You should try DbUnit for backup and restore of database.Here is the demo code for that:
try {
Class.forName(DBDRIVER);
Connection jdbcConnection = DriverManager.getConnection(DBURL, DBUSERNAME, DBPASSWORD);
IDatabaseConnection connection = new DatabaseConnection(jdbcConnection);
connection.getConfig().setProperty(DatabaseConfig.PROPERTY_DATATYPE_FACTORY,
new MySqlDataTypeFactory());
//////// Database backup
ITableFilter filter = new DatabaseSequenceFilter(connection);
IDataSet dataset = new FilteredDataSet(filter, connection.createDataSet());
ExcludeTableFilter excludeFilter = new ExcludeTableFilter();
excludeFilter.excludeTable("DATABASECHANGELOG*");
IDataSet excludedataset = new FilteredDataSet(excludeFilter, dataset);
FlatXmlDataSet.write(excludedataset, new FileOutputStream(backupfilename));
System.out.println("\n Complete backup successful.");
//////// Database backup
//////// Database restore
IDataSetProducer producer = new FlatXmlProducer(new InputSource(restoreFileName));
IDataSet dataSet = new StreamingDataSet(producer);
TransactionOperation operation = new TransactionOperation(DatabaseOperation.INSERT);
operation.execute(connection, dataSet);
//////// Database restore
} catch (DatabaseUnitException e) {
e.printStackTrace();
flag = false;
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
Use the same dump to import like this.
Process runProcess = Runtime.getRuntime().exec("C:\\SCM Files\\SQL Backup\\mysqldump.exe -uroot -p123 rr database_name < "C:\\SCM Files\\SQL Backup\\RR.sql");
For restore use the executeCmd in the form m.Torkashvand provided (array of strings). A working example on how to use these commands from JSP code can be found here
public static void mysqlExport(String host, String port, String user, String password, String dbname, String table, String folder, String query) {
System.out.println("------ Exporting "+dbname+"."+table+" at "+folder+"---------------------------");
try {
String command = "mysqldump --host=" + host + " --port=" + port + " --user=" + user + " --password=" + password + " " + dbname + " " + table + " --where=\"" + query + "\" > " + folder + table + ".sql";
System.out.println(command);
int returnValue = executeCommand(Arrays.asList("mysqldump", "--host="+host, "--port="+port, "--user="+user, "--password="+password, dbname, table, "--where="+query), folder + table + ".sql");
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
public static void mysqlImport(String host, String port, String user, String password, String dbname, String table, String folder) {
System.out.println("------ Importing "+dbname+"."+table+" at "+folder+"---------------------------");
try {
String command = "mysql --host=" + host + " --port=" + port + " --user=" + user + " --password=" + password + " " + dbname + " " + table + " < " + folder + table + ".sql";
System.out.println(command);
int returnValue = executeCommand(new String[]{"mysql", "--host="+host, "--port="+port, "--user=" + user, "--password=" + password, dbname, "-e", "source " + folder + table + ".sql"});
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
public static int executeCommand(String[] commands) throws IOException
{
System.out.println(commands.toString());
Process process = Runtime.getRuntime().exec(commands);
return dumpProcess(process);
}
public static int executeCommand(List<String> commands, String folder) throws IOException
{
ProcessBuilder builder = new ProcessBuilder(commands);
System.out.println(builder.command());
builder.redirectOutput(new File(folder));
Process process = builder.start();
return dumpProcess(process);
}
public static int dumpProcess(Process process) throws IOException
{
int returnValue = -1;
try {
String s = null;
process.waitFor();
returnValue = process.exitValue();
if (returnValue == 0) {
System.out.println("Command successful !!");
BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
System.out.println("Here is the standard output of the command:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
} else {
System.out.println("Command failed. Exist Status code = "+returnValue);
BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
return returnValue;
}
This is working code
public class Recover {
final static String filepath = "/home/shubhampanchal/Downloads/backup/configuration_files.sql";
public static void main(String[] args) throws Exception {
try {
String[] restoreCmd = new String[]{"mysql", "-uroot", "-p1", "Student", "-e", "source " + filepath};
Runtime rt =Runtime.getRuntime();
rt.exec(restoreCmd);
System.out.println("Restored successfully!");
} catch(Exception e) {
e.printStackTrace();
}
}
}
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
read/write to Windows Registry using Java
I want to read the registry value of the path HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS\CurrentVersion\Uninstall\{2FC099BD-AC9B-33EB-809C-D332E1B27C40}.
Can you please help me with the code?
This shows how to read the registry, but could be extended to write operations: How to read the Windows Registry
import java.io.*;
public class RegQuery {
private static final String REGQUERY_UTIL = "reg query ";
private static final String REGSTR_TOKEN = "REG_SZ";
private static final String REGDWORD_TOKEN = "REG_DWORD";
private static final String PERSONAL_FOLDER_CMD = REGQUERY_UTIL +
"\"HKCU\\Software\\Microsoft\\Windows\\CurrentVersion\\"
+ "Explorer\\Shell Folders\" /v Personal";
private static final String CPU_SPEED_CMD = REGQUERY_UTIL +
"\"HKLM\\HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0\""
+ " /v ~MHz";
private static final String CPU_NAME_CMD = REGQUERY_UTIL +
"\"HKLM\\HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0\""
+ " /v ProcessorNameString";
public static String getCurrentUserPersonalFolderPath() {
try {
Process process = Runtime.getRuntime().exec(PERSONAL_FOLDER_CMD);
StreamReader reader = new StreamReader(process.getInputStream());
reader.start();
process.waitFor();
reader.join();
String result = reader.getResult();
int p = result.indexOf(REGSTR_TOKEN);
if (p == -1)
return null;
return result.substring(p + REGSTR_TOKEN.length()).trim();
}
catch (Exception e) {
return null;
}
}
public static String getCPUSpeed() {
try {
Process process = Runtime.getRuntime().exec(CPU_SPEED_CMD);
StreamReader reader = new StreamReader(process.getInputStream());
reader.start();
process.waitFor();
reader.join();
String result = reader.getResult();
int p = result.indexOf(REGDWORD_TOKEN);
if (p == -1)
return null;
// CPU speed in Mhz (minus 1) in HEX notation, convert it to DEC
String temp = result.substring(p + REGDWORD_TOKEN.length()).trim();
return Integer.toString
((Integer.parseInt(temp.substring("0x".length()), 16) + 1));
}
catch (Exception e) {
return null;
}
}
public static String getCPUName() {
try {
Process process = Runtime.getRuntime().exec(CPU_NAME_CMD);
StreamReader reader = new StreamReader(process.getInputStream());
reader.start();
process.waitFor();
reader.join();
String result = reader.getResult();
int p = result.indexOf(REGSTR_TOKEN);
if (p == -1)
return null;
return result.substring(p + REGSTR_TOKEN.length()).trim();
}
catch (Exception e) {
return null;
}
}
static class StreamReader extends Thread {
private InputStream is;
private StringWriter sw;
StreamReader(InputStream is) {
this.is = is;
sw = new StringWriter();
}
public void run() {
try {
int c;
while ((c = is.read()) != -1)
sw.write(c);
}
catch (IOException e) { ; }
}
String getResult() {
return sw.toString();
}
}
public static void main(String s[]) {
System.out.println("Personal directory : "
+ getCurrentUserPersonalFolderPath());
System.out.println("CPU Name : " + getCPUName());
System.out.println("CPU Speed : " + getCPUSpeed() + " Mhz");
}
}
There's a tutorial that shows you without using Runtime.exec() function and uses specifically java.util.prefs.WindowsPreferences.