在 Java 中编写 .properties 文件会破坏文件的结构

Question

我可以使用此代码成功写入 Java .properties 文件：

Properties prop = new Properties();
prop.load(input);
prop.setProperty("myProp", "myValue");
prop.store(output, "");

但是当我查看我的.properties 文件时，所有结构都消失了！字段是按随机顺序写入的，所有的 cmets（我费了很大力气写）都被什么都覆盖了！

如何写入.properties 文件，同时确保其结构保持不变？

Answer 1

你可以使用Apache Commons Configuration 2:

<dependency>
  <groupId>org.apache.commons</groupId>
  <artifactId>commons-configuration2</artifactId>
  <version>2.1.1</version>
</dependency>

输入文件demo.properties:

# This is the file header
#
# Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna
# aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

# Database user
db.user=admin

# Database password
db.password=password

# Database URL
db.url=localhost

# This is the file footer
#
# Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
# occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

演示应用程序读取、修改和写入新的属性文件：

import org.apache.commons.configuration2.PropertiesConfiguration;
import org.apache.commons.configuration2.PropertiesConfigurationLayout;
import org.apache.commons.configuration2.ex.ConfigurationException;

import java.io.*;

class PropertiesFileWithCommentsDemo {
  public static void main(String[] args) throws IOException, ConfigurationException {
    // Load existing properties file
    File file = new File("demo.properties");
    PropertiesConfiguration config = new PropertiesConfiguration();
    PropertiesConfigurationLayout layout = new PropertiesConfigurationLayout();
    layout.load(config, new InputStreamReader(new FileInputStream(file)));

    // Print some information from the properties file
    System.out.println(layout.getHeaderComment());
    System.out.println(layout.getKeys());
    System.out.println(layout.getFooterComment());

    // Change existing property
    config.setProperty("db.password", "secret");

    // Add new property + comment + leading blank line
    config.setProperty("new.property", "Hello world!");
    layout.setComment("new.property", "This is a newly added property");
    layout.setBlancLinesBefore("new.property", 1);

    // Save to new properties file
    layout.save(config, new FileWriter("demo-append.properties", false));
  }
}

控制台日志：

# This is the file header
#
# Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna
# aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
[db.user, db.password, db.url]

# This is the file footer
#
# Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
# occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

输出文件demo-append.properties:

# This is the file header
#
# Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna
# aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

# Database user
db.user=admin

# Database password
db.password=secret

# Database URL
db.url=localhost

# This is a newly added property
new.property = Hello world!

# This is the file footer
#
# Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
# occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.