I have the following package hierarchy:
base--images--img.png
|
--code--Foo.java
|
--Base.java
That is, I have a package base which has 2 subpackages, base.images and base.code with respective files in each. Base.java just calls a method in Foo.
All of this gets bundled into base.jar when I build.
The problem: How can Foo.java load img.png no matter where the jar is located or run from?
Some things I've tried:
new File("../images/img.png")
Foo.class.getResource("../images/img.png")
Neither of these work because the "../images/img.png" is appended to the path the JAR is run from, not the path of the class.
MWE:
In Foo.java:
package base.code;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
public class Foo {
public static void main(String[] args) {
URL url = Foo.class.getResource("/graphs/1.png");
try {
BufferedImage img = ImageIO.read(url);
} catch (IOException e) {
System.err.println("Image not found!");
}
}
}
In Base.java:
package base;
public class Base {
public static void main(String[] args)
Foo.main(args);
}
}
Resources are on the class path, never use a File. They might be stored in the jar (zip format).
The solution is simply to use an absolute path. That is more clear than a class package's relative path.
Foo.class.getResource("/base/images/img.png")
Related
I want to create a Java class that I use to export images. This class will be exported in .JAR file which will allow me to integrate it directly into another project by passing as input parameter the name of the file and in return I would have this image in PNG format.
That's what I tried:
package militarySymbolsLibrary;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class MainEntry {
public static void main(String agrs[]) {
}
public static BufferedImage generateImage(String symbolCode) {
File imageFile = new File("/pictures/SSGPU-------.png");
BufferedImage image;
try {
image = ImageIO.read(imageFile);
} catch (IOException e) {
image = null;
e.printStackTrace();
}
return image;
}
}
Pictures are stocked in folder pictures like this treeview below:
src
MainEntry.java
pictures
SSGPU-------.png
Then I export this class in .JAR file, I add it to my other program, I pass a parameter (picture's name except for this test) and normally my class return PNG file. But I have an error telling me that the file path is not the rigth one.
How can I solve this problem?
Thank you
The following code is for reading or writing files with java, but:
Eclipse prints these errors:
buffer_1 cannot be resolved to a variable
file_reader cannot be resolved
also other attributes...
what is wrong in this code here:
//Class File_RW
package R_2;
import java.io.File;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.lang.NullPointerException;
public class File_RW {
public File_RW() throws FileNotFoundException, NullPointerException {
File file_to_read = new File("C:/myfiletoread.txt");
FileReader file_reader = new FileReader(file_to_read);
int nr_letters = (int)file_to_read.length()/Character.BYTES;
char buffer_1[] = new char[nr_letters];
}
public void read() {
file_reader.read(buffer_1, 0, nr_letters);
}
public void print() {
System.out.println(buffer_1);
}
public void close() {
file_reader.close();
}
public File get_file_to_read() {
return file_to_read;
}
public int get_nr_letters() {
return nr_letters;
}
public char[] get_buffer_1() {
return buffer_1;
}
//...
}
//main method # class Start:
package R_2;
import java.io.File;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.lang.NullPointerException;
public class Start {
public static void main(String[] args) {
File_RW file = null;
try {
file = new File_RW();
} catch (NullPointerException e_1) {
System.out.println("File not found.");
}
//...
}
}
I can't find any mistake. I have also tried to include a try catch statement into the constructor of the class "File_RW", but the error messages were the same.
Yes, there are errors in your code - which are of really basic nature: you are declaring variables instead of fields.
Meaning: you have them in the constructor, but they need to go one layer up! When you declare an entity within a constructor or method, then it is a variable that only exists within that constructor/method.
If you want that multiple methods can make use of that entity, it needs to be a field, declared in the scope of the enclosing class, like:
class FileRW {
private File fileToRead = new File...
...
and then you can use your fields within all your methods! Please note: you can do the actual setup within your constructor:
class FileRW {
private File fileToRead;
public FileRW() {
fileToRead = ..
but you don't have to.
Finally: please read about java language conventions. You avoid using "_" within names (just for SOME_CONSTANT)!
javacode already running...thx
same program edited with c++ in visual Studio express...
visit the stackoverflow entry link:
c++ file read write-error: Microsoft Visual C++ Runtime libr..debug Assertion failed, expr. stream.valid()
I have the file allDepartments.json in a subdirectory called fixtures, to which I want to access from the Fixture.java class.
This is my Fixture.java code:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
public final class Fixture {
private static final String FIXTURES_PATH = "";
private final String fixture;
public Fixture(String fixtureName) throws IOException {
fixture = new String(Files.readAllBytes(Paths.get(FIXTURES_PATH + fixtureName)));
}
public final String getFixture() {
return fixture;
}
}
However every time he tries to access the file I get a java.nio.file.NoSuchFileException: allDepartments.json...
I have heard of the getResource() method and tried every combination possible of it, without success.
I need this to store multi-line strings for my JUnit tests.
What can I do?
The NIO.2 API can't be used to read files that are effectively project resources, i.e. files present on the classpath.
In your situation, you have a Maven project and a resource that you want to read during the unit test of the application. First, this implies that this resources should be placed under src/test/resources so that Maven adds it automatically to the classpath during the tests. Second, this implies that you can't use the Files utility to read it.
You will need to resort to using a traditional BufferedReader:
public Fixture(String fixtureName) throws IOException {
try (BufferedReader br = new BufferedReader(new InputStreamReader(Fixture.class.getResourceAsStream(FIXTURES_PATH + fixtureName)))) {
// do your thing with br.readLine();
}
}
Note the path given to getResourceAsStream is either relative to the current class or absolute. If the resources is located in src/test/resources/folder/allDepartments.json then a valid path would be /folder/allDepartments.json.
Add allDepartments.json to the.classpath file of the project and java should be able to pick it up.
Refer this topic if you want to know how to add a file to class path from eclipse
when you run Fixtures.java the relative path would be
../fixtures/allDepartments.json
try using this path.
Thank you all for helping and suggestions.
Thanks to you I was able to put things working, so here is the trick (which I guess only works for Maven projects):
I moved the allDepartments.json file to the default src/test/resources folder as suggested by you guys. I didn't even had to modify the pom.xml. And now everything works!
So this is my project structure now:
And the final Fixture.java code is:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.stream.Collectors;
public final class Fixture {
private final String fixture;
public Fixture(String fixtureName) throws IOException {
fixture = this.readFile(fixtureName);
}
private String readFile(String fileName) throws IOException {
final InputStream in = this.getClass().getClassLoader().getResource("fixtures/" + fileName).openStream();
final BufferedReader buffer = new BufferedReader(new InputStreamReader(in));
try {
return buffer.lines().collect(Collectors.joining("\n"));
} finally {
buffer.close();
}
}
public final String getFixture() {
return fixture;
}
}
I need put one specific image from my project to specific folder in Java. Thanks for helping.
Edit:
Im creating a folder with File and the folder I'm creating i need to put an image i have in resources. Thanks for helping.
You can use NIO package in Java 7 with the class Files and the static method copy.
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
public class Main_copie {
public static void main(String[] args) {
Path source = Paths.get("data/image1.png");
Path destination = Paths.get("MyFolder/image1_copied.png");
try {
Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Do you mean to copy the file from 1 location to another? If so, then the approach would be to create a new File at the desired location, create a FileOutputStream and write everything from the original File (using an FileInputStream) to this OutputStream.
Maybe this post can help you out.
I have a requirement to capture photos using system webcam. For this, I'm using webcam capture library. It contained three jar files. I wanted to package every thing including dependency jars in single jar application.
So, I sorted to unpack the dependent jar files place them in the src folder of netbeans project.
So, I extracted them. Two of them start with the same package name org, so I extracted and merged them. Important third package starts with com package. I've placed these three directories in src folder of my netbeans project.
Now the problem is that netbeans, says that package doesn't exist. But, the same project when compiled from command line in windows. It compiled and ran successfully, everything was working fine.
But, when I added the problematic library as a jar to the project, it worked fine, only extracting and placing it in src folder causing the problem.
Why is this error occurring and why in netbeans only, how to resolve this problem?
My code:
package screen;
import com.github.sarxos.webcam.*; **//Error here**
import com.github.sarxos.webcam.log.*; **// Error here**
import java.io.*;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
public class Util extends TimerTask{
private String filePath;
private String type;
private Timer timer;
private Webcam webcam;
public Util(String path,String type){
this.timer=new Timer("Capture Timer");
this.filePath=path;
this.type=type;
this.webcam=Webcam.getDefault();
}
public void capture() throws IOException{
if(webcam!=null){
webcam.open();
BufferedImage image=webcam.getImage();
Date date=new Date();
ImageIO.write(image,type,new File(filePath+"_"+date.toString().replace(' ','_').replace(':','-')+"."+type.toLowerCase()));
webcam.close();
}
else{
webcam=Webcam.getDefault();
}
}
public void startCapturing(int period){
this.timer.schedule(this,0,period);
}
public void stopCapturing(){
timer.cancel();
}
public void run(){
try{
capture();
System.out.println("Doing");
}catch(Exception e){
e.printStackTrace();
}
}
public static void main(String args[]){
Util u=new Util("n082430_","PNG");
u.startCapturing(60000);
}
}