如何通过提及关键字仅在第一次出现时替换特定行

Question

I have below pom.xml file. I want to replace the version of the project which is in line 7. I will be able to provide <version> tag alone but not complete version details. Expecting a code which finds the 1st <version> tag line and replace that with <version>1.0.1</version>

I started with the below java code but which is currently replacing the whole version tag in the entire pom.xml.

How do I replace 1st <version> tag line alone with <version>1.0.1</version>

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.myspace</groupId>
  <artifactId>Test</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>kjar</packaging>
  <name>Test</name>
  <description></description>
  <dependencies>
    <dependency>
      <groupId>org.kie</groupId>
      <artifactId>kie-api</artifactId>
      <version>7.46.0.Final</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.kie</groupId>
      <artifactId>kie-internal</artifactId>
      <version>7.46.0.Final</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.optaplanner</groupId>
      <artifactId>optaplanner-core</artifactId>
      <version>7.46.0.Final</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.optaplanner</groupId>
      <artifactId>optaplanner-persistence-jaxb</artifactId>
      <version>7.46.0.Final</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.thoughtworks.xstream</groupId>
      <artifactId>xstream</artifactId>
      <version>1.4.11.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.kie</groupId>
        <artifactId>kie-maven-plugin</artifactId>
        <version>7.46.0.Final</version>
        <extensions>true</extensions>
      </plugin>
    </plugins>
  </build>
</project>

Java code

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class OverwriteLine {
   public static void main(String args[]) throws IOException {
      //Instantiating the File class
      String cloneDirectoryPath = "D:\\project\\localrepo117";
      String filePath = cloneDirectoryPath+"\\pom.xml";
      //Instantiating the Scanner class to read the file
      Scanner sc = new Scanner(new File(filePath));
      //instantiating the StringBuffer class
      StringBuffer buffer = new StringBuffer();
      //Reading lines of the file and appending them to StringBuffer
      while (sc.hasNextLine()) {
         buffer.append(sc.nextLine()+System.lineSeparator());
      }
      String fileContents = buffer.toString();
      System.out.println("Contents of the file: "+fileContents);
      //closing the Scanner object
      sc.close();
      String oldLine = "<version>";
      String newLine = "<version>1.0.1</version>";
      //Replacing the old line with new line
      fileContents = fileContents.replaceAll(oldLine, newLine);
      //instantiating the FileWriter class
      FileWriter writer = new FileWriter(filePath);
      System.out.println("");
      System.out.println("new data: "+fileContents);
      writer.append(fileContents);
      writer.flush();
   }
}

Answer 1

I suggest that you read file "pom.xml", line by line. If the line read is the line you want to change, then change it otherwise leave it as it is. Then write the line that you read to a temporary file. Once you have read all the lines in file "pom.xml", delete it and rename the temporary file to "pom.xml".

The below code does this.

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;

public class OverwriteLine {

    public static void main(String[] args) {
        Path sourcePath = Path.of("pom.xml");
        Path targetPath = Path.of("tmp.xml");
        boolean error = false;
        try (BufferedReader br = Files.newBufferedReader(sourcePath);
             BufferedWriter bw = Files.newBufferedWriter(targetPath,
                                                         StandardOpenOption.CREATE,
                                                         StandardOpenOption.TRUNCATE_EXISTING,
                                                         StandardOpenOption.WRITE)) {
            boolean found = false;
            String line = br.readLine();
            while (line != null) {
                if (!found) {
                    if (line.trim().startsWith("<version>")) {
                        found = true;
                        line = line.replace("1.0.0", "1.0.1");
                    }
                }
                bw.write(line);
                bw.write(System.lineSeparator());
                line = br.readLine();
            }
        }
        catch (IOException xIo) {
            error = true;
            xIo.printStackTrace();
        }
        if (!error) {
            try {
                Files.delete(sourcePath);
                Files.move(targetPath, sourcePath);
            }
            catch (IOException xIo) {
                xIo.printStackTrace();
            }
        }
    }
}