How to format message with argument names instead of numbers?

I have something like:

String text = "The user {0} has email address {1}."
// params = { "Robert", "myemailaddr@gmail.com" }
String msg = MessageFormat.format(text, params);

This isn't great for me, because sometimes my translators are not sure what goes in the {0} and {1}, also it would be nice to be able to reword the messages without worrying about the order of the args.

I'd like开发者_如何转开发 to replace the arguments with readable names instead of numbers. Something like this:

String text = "The user {USERNAME} has email address {EMAILADDRESS}."
// Map map = new HashMap( ... [USERNAME="Robert", EMAILADDRESS="myemailaddr@gmail.com"]
String msg = MessageFormat.format(text, map);

Is there an easy way to do this?

Thanks! rob

You can use MapFormat for this. Find out the details here:

http://www.java2s.com/Code/Java/I18N/AtextformatsimilartoMessageFormatbutusingstringratherthannumerickeys.htm

String text = "The user {name} has email address {email}.";
Map map = new HashMap();
map.put("name", "Robert");
map.put("email", "rhume55@gmail.com");

System.out.println("1st : " + MapFormat.format(text, map));

OUTPUT:

1st : The user Robert has email address rhume55@gmail.com.

See StrSubstitutor from org.apache.commons.lang3:

Map valuesMap = HashMap();
valuesMap.put("animal", "quick brown fox");
valuesMap.put("target", "lazy dog");
String templateString = "The ${animal} jumped over the ${target}.";
StrSubstitutor sub = new StrSubstitutor(valuesMap);
String resolvedString = sub.replace(templateString);

// resolvedString: "The quick brown fox jumped over the lazy dog."

Easy to make one yourself. This is what I use (the main() function is just for test code):

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StringTemplate {
    final private String template;
    final private Matcher m;
    static final private Pattern keyPattern = 
        Pattern.compile("\\$\\{([a-zA-Z][a-zA-Z0-9_]*(\\.[a-zA-Z][a-zA-Z0-9_]*)*)\\}");
    private boolean blanknull=false;

    public StringTemplate(String template) { 
        this.template=template;
        this.m = keyPattern.matcher(template);
    }

    /**
     * @param map substitution map
     * @return substituted string
     */
    public String substitute(Map<String, ? extends Object> map)
    {
        this.m.reset();
        StringBuffer sb = new StringBuffer();
        while (this.m.find())
        {
            String k0 = this.m.group();
            String k = this.m.group(1);
            Object vobj = map.get(k);
            String v = (vobj == null) 
                ? (this.blanknull ? "" : k0)
                : vobj.toString();
            this.m.appendReplacement(sb, Matcher.quoteReplacement(v));
        }
        this.m.appendTail(sb);
        return sb.toString();       
    }

    public StringTemplate setBlankNull()
    {
        this.blanknull=true;
        return this;
    }

    static public void main(String[] args)
    {
        StringTemplate t1 = new StringTemplate("${this} is a ${test} of the ${foo} bar=${bar} ${emergency.broadcasting.system}");
        t1.setBlankNull();
        Map<String, String> m = new HashMap<String, String>();
        m.put("this", "*This*");
        m.put("test", "*TEST*");
        m.put("foo", "$$$aaa\\\\111");
        m.put("emergency.broadcasting.system", "EBS");
        System.out.println(t1.substitute(m));
    }
}

Your question is closely related to: How to replace a set of tokens in a Java String You could use velocity or another template library. But there will be some pain because Java does not have any kind of Map literals.

I know my answer comes a little late, but if you still need this functionality, without the need to download a full-fledged template engine you can take a look at aleph-formatter (I am one of the authors):

Student student = new Student("Andrei", 30, "Male");

String studStr = template("#{id}\tName: #{st.getName}, Age: #{st.getAge}, Gender: #{st.getGender}")
                    .arg("id", 10)
                    .arg("st", student)
                    .format();
System.out.println(studStr);

Or you can chain the arguments:

String result = template("#{x} + #{y} = #{z}")
                    .args("x", 5, "y", 10, "z", 15)
                    .format();
System.out.println(result);

// Output: "5 + 10 = 15"

Internally it works using a StringBuilder creating the result by "parsing" the expression, no string concatenation, regex/replace is performed.

static final Pattern REPLACE_PATTERN = Pattern.compile("\\x24\\x7B([a-zA-Z][\\w\\x2E].*?)\\x7D");

/**
 * Check for unresolved environment
 *
 * @param str
 * @return origin if all substitutions resolved
 */
public static String checkReplacement(String str) {
    Matcher matcher = REPLACE_PATTERN.matcher(str);
    if (matcher.find()) {
        throw LOG.getIllegalArgumentException("Environment variable '" + matcher.group(1) + "' is not defined");
    }
    return str;
}

// replace in str ${key} to value
public static String resolveReplacement(String str, Map<String, String> replacements) {
    Matcher matcher = REPLACE_PATTERN.matcher(str);
    while (matcher.find()) {
        String value = replacements.get(matcher.group(1));
        if (value != null) {
            str = matcher.replaceFirst(replaceWindowsSlash(value));
        }
    }
    return str;
}

But you loose all format options (like ##.#)