JAVA如何在Project中引用文件

Question

I am create a simple Java Project in my VS Code, and here is the project structure.

I want to refer the wordcount.txt in my code, but it fail to find the file.

Here is my test code:

public class BatchJob {

public static void main(String[] args) throws Exception {
    // set up the batch execution environment
    final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
    //URL url = BatchJob.class.getClassLoader().getResource("resources/wordcount.txt");
    DataSource<String> dataset = env.readTextFile("wordcount.txt");
    DataSet<Tuple2<String, Integer>> result = dataset.flatMap(new Tokenizer())
                                                    .filter(new FilterFunction<Tuple2<String, Integer>>(){
                                                        @Override
                                                        public boolean filter(Tuple2<String, Integer> arg0){
                                                            return arg0.f1 >0;
                                                        }
                                                    })
                                                    .groupBy(0)
                                                    .sum(1);
                                                    result.print();
    
}
public static class Tokenizer implements FlatMapFunction<String, Tuple2<String, Integer>>{
    @Override
    public void flatMap(String value, Collector<Tuple2<String, Integer>> out) throws Exception {
        String[] tokens = value.toLowerCase().split(",");
        for (String token : tokens) {
            if ( !token.isEmpty() && token.length() > 0) {
                out.collect(new Tuple2<String, Integer>(token, 1));
            }
        }
    }
}

}

Answer 1

Application resources will become embedded resources by the time of deployment, so it is wise to start accessing them as if they were, right now. An embedded-resource must be accessed by URL rather than file . See the info. page for embedded resource for how to form the URL.

Thanks for your work, work with getResource . Here is the working code

URL url = BatchJob.class.getClassLoader().getResource("wordcount.txt"); DataSource<String> dataset = env.readTextFile( URLDecoder.decode(url.getFile(),"UTF-8") );

Unfortunately, this fix goes wrong at url.getFile() .

Harking back to the bold part of the original advice.. ".. must be accessed by URL rather than file" : This is not a suggestion or merely a good programming practice, it is a requirement. The thing is, once the app. is built, the resource will be inside a Jar and will not be a File any longer. It will not be accessible as a File . So while it might work when running it from the IDE (when the URL points to something that is a file), it will fail for the built Jar.