Java Properties object to String

Question

I have a Java Properties object that I load from an in-memory String, that was previously loaded into memory from the actual .properties file like this:

this.propertyFilesCache.put(file, FileUtils.fileToString(propFile));

The util fileToString actually reads in the text from the file and the rest of the code stores it in a HashMap called propertyFilesCache. Later, I read the file text from the HashMap as a String and reload it into a Java Properties object like so:

String propFileStr = this.propertyFilesCache.get(fileName);
Properties tempProps = new Properties();
try {
    tempProps.load(new ByteArrayInputStream(propFileStr.getBytes()));
} catch (Exception e) {
    log.debug(e.getMessage());
}
tempProps.setProperty(prop, propVal);

At this point, I've replaced my property in my in-memory property file and I want to get the text from the Properties object as if I was reading a File object like I did up above. Is there a simple way to do this or am I going to have to iterate over the properties and create the String manually?

lsiu · Accepted Answer · 2009-10-16 16:57:54Z

32

public static String getPropertyAsString(Properties prop) {    
  StringWriter writer = new StringWriter();
  prop.list(new PrintWriter(writer));
  return writer.getBuffer().toString();
}

answered Oct 16, 2009 at 16:57

lsiu

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2 Comments

Spanky Quigman Over a year ago

It's worth noting that this will not give you a straight rendering of the properties back, i.e. you can't just pop out that string into a file and load it back as a properties file. This is because that Properties.list() method prepends a header onto the list: -- listing properties -- More likely you'd want to use the Properties.store() method described in the comment from @joev comment below.

abbath0767 Over a year ago

bad and ugly recomendation because this have unexcepted beahviour: (var5.length() > 40) and

Banana · Accepted Answer · 2013-08-21 15:16:51Z

18

There seems to be a problem with @Isiu answer. After that code Properties are truncated, like there is some limit to string length. Proper way is to use code like this:

public static String getPropertyAsString(Properties prop) { 
    StringWriter writer = new StringWriter();
    try {
        prop.store(writer, "");
    } catch (IOException e) {
        ...
    }
    return writer.getBuffer().toString();
}

answered Aug 21, 2013 at 15:16

Banana

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1 Comment

selle Over a year ago

You get a header with a time stamp with that method.

maestr0 · Accepted Answer · 2012-07-04 13:59:15Z

9

It's not directly related to your question but if you just want to print out properties for debugging you can do something like this

properties.list(System.out);

answered Jul 4, 2012 at 13:59

maestr0

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1 Comment

heez Over a year ago

Or even just call .toString() if you're using a logging solution. It uses ConcurrentHashMaps implementation.

nybon · Accepted Answer · 2018-06-08 23:05:07Z

6

If you are using Java 8 or above, here is a single statement solution with the possibility to control the format by yourself:

String properties = System.getProperties().entrySet()
            .stream()
            .map(e -> e.getKey() + ":" + e.getValue())
            .collect(Collectors.joining(", "));

answered Jun 8, 2018 at 23:05

nybon

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Comments

joev · Accepted Answer · 2009-10-16 16:51:28Z

2

I don't completely understand what you're trying to do, but you can use the Properties class' store(OutputStream out, String comments) method. From the javadoc:

public void store(OutputStream out, String comments) throws IOException

Writes this property list (key and element pairs) in this Properties table to the output stream in a format suitable for loading into a Properties table using the load(InputStream) method.

answered Oct 16, 2009 at 16:51

joev

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Comments

Sam YC · Accepted Answer · 2018-04-30 10:55:05Z

1

You can do as below also:

Properties p = System.getProperties();
Enumeration keys = p.keys();
while (keys.hasMoreElements()) {
    String key = (String)keys.nextElement();
    String value = (String)p.get(key);
    System.out.println(key + ": " + value);
}

answered Apr 30, 2018 at 10:55

Sam YC

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Comments

Moebius · Accepted Answer · 2014-08-12 12:24:57Z

0

Another function to print all the values of a field is :

public static <T>void   printFieldValue(T obj)
{
    System.out.printf("###" + obj.getClass().getName() + "###");
    for (java.lang.reflect.Field field : obj.getClass().getDeclaredFields()) {
        field.setAccessible(true);
        String name = field.getName();
        Object value = null;
        try{
            value = field.get(obj);
        }catch(Throwable e){}
        System.out.printf("#Field name: %s\t=> %s%n", name, value);
    }
}

answered Aug 12, 2014 at 12:24

Moebius

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Comments

agabrys · Accepted Answer · 2021-01-20 23:03:53Z

Using the list method is incorrect because it should be used only for debugging purposes

Prints this property list out to the specified output stream. This method is useful for debugging.

It doesn't escape keys which contains special characters, like = or :.

The store method should be used, but it inserts a comment and timestamp. The following code removes these additional lines and returns a text with normalized new lines.

Java

public static String propertiesToString(Properties properties) throws IOException {
    if (properties == null) {
        return null;
    }
    if (properties.isEmpty()) {
        return "";
    }
    StringWriter writer = new StringWriter();
    properties.store(writer, null);
    String text = normalizeNewLines(writer.toString());
    List<String> lines = new ArrayList<>(Arrays.asList(text.split("\n")));
    lines.remove(0);
    return lines.stream().collect(Collectors.joining("\n"));
}

private static String normalizeNewLines(String text) {
    return text.replace("\r\n", "\n").replace("\r", "\n");
}

Groovy

static String propertiesToString(Properties properties) {
    if (properties.is(null)) {
        return null
    }
    if (properties.isEmpty()) {
        return ''
    }
    def writer = new StringWriter()
    properties.store(writer, null)
    def lines = normalizeNewLines(writer).split('\n') as List
    lines.remove(0)
    return lines.join('\n')
}

private static String normalizeNewLines(String text) {
    return text.replace('\r\n', '\n').replace('\r', '\n')
}

Dyadko · Accepted Answer · 2025-03-25 14:49:40Z

0

Properties properties;
new HashMap<>(properties).toString()
    .replace(',', '\r');

without values truncation. The replace call is for the case if you want to list properties in a column.

answered Mar 25 at 14:49

Dyadko

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