Intro
In this time, I will try getting file list from specified directory.
And I only retrieve the files what has the specific extension.
The root directory path and file extensions are gotten from a JSON file.
Environments
- Amazon Corretto ver.21.0.3.9.1
- Gradle ver.8.4
Reading a JSON file
First, I put a JSON file what is named "appsettings.json" into src/main/resources.
appsettings.json
{
"rootDir": "C:/Users/example/OneDrive/Documents/sample",
"extensions": ["pdf", "xlsx"]
}
I will read it and convert to a Java object by Jackson.
build.gradle
plugins {
id 'application'
}
repositories {
mavenCentral()
}
dependencies {
implementation 'com.fasterxml.jackson.core:jackson-databind:2.17.1'
testImplementation 'junit:junit:4.13.2'
implementation 'com.google.guava:guava:32.1.1-jre'
}
java {
toolchain {
languageVersion = JavaLanguageVersion.of(21)
}
}
application {
mainClass = 'jp.masanori.fileremover.App'
}
tasks.withType(JavaCompile) {
options.encoding = 'UTF-8'
}
AppSetting.java
package jp.masanori.fileremover.Apps;
public class AppSetting {
public String rootDir;
public String[] extensions;
}
Appsettings.java
package jp.masanori.fileremover.Apps;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import jp.masanori.fileremover.App;
public class AppSettings {
public static AppSetting load() {
try {
String filePathText = App.class.getClassLoader().getResource("appsettings.json").getPath();
// Because the path starts from "/" like "/C:/Users/example/~", I will remove the first "/".
Path filePath = Paths.get(filePathText.substring(1, filePathText.length()));
byte[] fileData = Files.readAllBytes(filePath);
ObjectMapper objectMapper = new ObjectMapper();
// Convert
return objectMapper.readValue(fileData, AppSetting.class);
}catch(JsonProcessingException ex) {
System.out.println("[JsonProcessingException] " + ex.getLocalizedMessage());
} catch(IOException ex) {
System.out.println("[IOException] " + ex.getLocalizedMessage());
}
return null;
}
}
Getting file list
FileController.java
package jp.masanori.fileremover.Files;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import jp.masanori.fileremover.Apps.ActionResult;
import jp.masanori.fileremover.Apps.AppSetting;
public class FileController {
public static ActionResult removeFiles(AppSetting settings) {
Path rootDirPath = Paths.get(settings.rootDir);
if(Files.exists(rootDirPath) == false) {
return ActionResult.getFailed("The root directory was not found");
}
Pattern pattern = generateFileExtensionPattern(settings.extensions);
try (Stream<Path> paths = Files.walk(rootDirPath)) {
List<Path> targetFilePaths = paths.filter(p -> Files.isDirectory(p) == false)
.filter(p -> pattern.matcher(p.toString()).find())
.collect(Collectors.toList());
for(Path p : targetFilePaths) {
System.out.println(p.toString());
}
} catch(IOException ex) {
System.out.println(ex.getLocalizedMessage());
return ActionResult.getFailed("Failed getting file lists");
}
return ActionResult.getSucceeded();
}
/** Generating a pattern like "\\.pdf|\\.xlsx" */
private static Pattern generateFileExtensionPattern(String[] fileExtensions) {
StringBuilder sb = new StringBuilder();
boolean first = true;
for(String extension : fileExtensions) {
if(first) {
first = false;
} else {
sb.append("|");
}
sb.append("\\.");
sb.append(extension);
sb.append("$");
}
return Pattern.compile(sb.toString());
}
}
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