如何通過提及關鍵字僅在第一次出現時替換特定行

Question

我有以下 pom.xml 文件。 我想替換第 7 行中的項目版本。我將能夠單獨提供<version>標記，但不能提供完整的版本詳細信息。 期望找到第一個<version>標記行並將其替換為<version>1.0.1</version>的代碼

我從下面的 java 代碼開始，但目前正在替換整個 pom.xml 中的整個版本標記。

如何用<version>1.0.1</version>單獨替換第一個<version>標記行

<?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 代碼

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

我建議您逐行閱讀文件“pom.xml”。 如果讀取的行是您要更改的行，則更改它，否則保持原樣。 然后將您讀取的行寫入臨時文件。 閱讀完文件“pom.xml”中的所有行后，將其刪除並將臨時文件重命名為“pom.xml”。

下面的代碼就是這樣做的。

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();
            }
        }
    }
}