org.coode.oppl.template.commons.KeyBasedReplacementStrategy Maven / Gradle / Ivy

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package org.coode.oppl.template.commons;

import static org.coode.oppl.utils.ArgCheck.checkNotNull;

import java.util.Properties;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.coode.oppl.template.ReplacementStrategy;

/** This strategy assumes that place-holders are also keys in a
 * {@link Properties} instance. It replaces them with their corresponding
 * values. The property names are the place-holders name without the
 * {@literal %} prefix
 * 
 * @author Luigi Iannone */
public final class KeyBasedReplacementStrategy implements
        ReplacementStrategy {
    private final Properties properties;

    /** @param properties
     *            properties */
    public KeyBasedReplacementStrategy(Properties properties) {
        this.properties = checkNotNull(properties, "properties");
    }

    @Override
    public String replace(String templateString) {
        // Non greedy matching
        Pattern pattern = Pattern.compile("\\$\\{(.+?)\\}");
        String replacedString = templateString;
        Matcher matcher = pattern.matcher(replacedString);
        while (matcher.find()) {
            String placeholder = matcher.group();
            String key = matcher.group(1);
            replacedString = replacedString.replaceAll(encode(placeholder),
                    getReplacement(key));
            matcher = pattern.matcher(replacedString);
        }
        return replacedString;
    }

    private String encode(String placeholder) {
        return placeholder.replaceAll("(\\$)", "\\\\$1").replaceAll("(\\{)", "\\\\$1")
                .replaceAll("(\\})", "\\\\$1");
    }

    private String getReplacement(String placeholder) {
        String replacement = properties.getProperty(placeholder);
        if (replacement == null) {
            throw new NullPointerException("Missing value for place-holder "
                    + placeholder);
        }
        return replacement;
    }
}