Template.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.calcite.util;
import com.google.common.collect.ImmutableList;
import org.checkerframework.checker.nullness.qual.Nullable;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
/**
* String template.
*
* <p>It is extended from {@link java.text.MessageFormat} to allow parameters
* to be substituted by name as well as by position.
*
* <p>The following example, using MessageFormat, yields "Happy 64th birthday,
* Ringo!":
*
* <blockquote>MessageFormat f =
* new MessageFormat("Happy {0,number}th birthday, {1}!");<br>
* Object[] args = {64, "Ringo"};<br>
* System.out.println(f.format(args);</blockquote>
*
* <p>Here is the same example using a Template and named parameters:
*
* <blockquote>Template f =
* new Template("Happy {age,number}th birthday, {name}!");<br>
* Map<Object, Object> args = new HashMap<Object, Object>();<br>
* args.put("age", 64);<br>
* args.put("name", "Ringo");<br>
* System.out.println(f.format(args);</blockquote>
*
* <p>Using a Template you can also use positional parameters:
*
* <blockquote>Template f =
* new Template("Happy {age,number}th birthday, {name}!");<br>
* Object[] args = {64, "Ringo"};<br>
* System.out.println(f.format(args);</blockquote>
*
* <p>Or a hybrid; here, one argument is specified by name, another by position:
*
* <blockquote>Template f =
* new Template("Happy {age,number}th birthday, {name}!");<br>
* Map<Object, Object> args = new HashMap<Object, Object>();<br>
* args.put(0, 64);<br>
* args.put("name", "Ringo");<br>
* System.out.println(f.format(args);</blockquote>
*/
public class Template extends MessageFormat {
private final List<String> parameterNames;
/**
* Creates a Template for the default locale and the
* specified pattern.
*
* @param pattern the pattern for this message format
* @throws IllegalArgumentException if the pattern is invalid
*/
public static Template of(String pattern) {
return of(pattern, Locale.getDefault());
}
/**
* Creates a Template for the specified locale and
* pattern.
*
* @param pattern the pattern for this message format
* @param locale the locale for this message format
* @throws IllegalArgumentException if the pattern is invalid
*/
public static Template of(String pattern, Locale locale) {
final List<String> parameterNames = new ArrayList<>();
final String processedPattern = process(pattern, parameterNames);
return new Template(processedPattern, parameterNames, locale);
}
private Template(
String pattern, List<String> parameterNames, Locale locale) {
super(pattern, locale);
this.parameterNames = ImmutableList.copyOf(parameterNames);
}
/**
* Parses the pattern, populates the parameter names, and returns the
* pattern with parameter names converted to parameter ordinals.
*
* <p>To ensure that the same parsing rules apply, this code is copied from
* {@link java.text.MessageFormat#applyPattern(String)} but with different
* actions when a parameter is recognized.
*
* @param pattern Pattern
* @param parameterNames Names of parameters (output)
* @return Pattern with named parameters substituted with ordinals
*/
private static String process(String pattern, List<String> parameterNames) {
StringBuilder[] segments = new StringBuilder[4];
for (int i = 0; i < segments.length; ++i) {
segments[i] = new StringBuilder();
}
int part = 0;
boolean inQuote = false;
int braceStack = 0;
for (int i = 0; i < pattern.length(); ++i) {
char ch = pattern.charAt(i);
if (part == 0) {
if (ch == '\'') {
segments[part].append(ch); // jhyde: don't lose orig quote
if (i + 1 < pattern.length()
&& pattern.charAt(i + 1) == '\'') {
segments[part].append(ch); // handle doubles
++i;
} else {
inQuote = !inQuote;
}
} else if (ch == '{' && !inQuote) {
part = 1;
} else {
segments[part].append(ch);
}
} else if (inQuote) { // just copy quotes in parts
segments[part].append(ch);
if (ch == '\'') {
inQuote = false;
}
} else {
switch (ch) {
case ',':
if (part < 3) {
part += 1;
} else {
segments[part].append(ch);
}
break;
case '{':
++braceStack;
segments[part].append(ch);
break;
case '}':
if (braceStack == 0) {
part = 0;
makeFormat(segments, parameterNames);
} else {
--braceStack;
segments[part].append(ch);
}
break;
case '\'':
inQuote = true;
// fall through, so we keep quotes in other parts
default:
segments[part].append(ch);
break;
}
}
}
if (braceStack == 0 && part != 0) {
throw new IllegalArgumentException(
"Unmatched braces in the pattern.");
}
return segments[0].toString();
}
/**
* Called when a complete parameter has been seen.
*
* @param segments Comma-separated segments of the parameter definition
* @param parameterNames List of parameter names seen so far
*/
private static void makeFormat(
StringBuilder[] segments,
List<String> parameterNames) {
final String parameterName = segments[1].toString();
final int parameterOrdinal = parameterNames.size();
parameterNames.add(parameterName);
segments[0].append("{");
segments[0].append(parameterOrdinal);
final String two = segments[2].toString();
if (two.length() > 0) {
segments[0].append(",").append(two);
}
final String three = segments[3].toString();
if (three.length() > 0) {
segments[0].append(",").append(three);
}
segments[0].append("}");
segments[1].setLength(0); // throw away other segments
segments[2].setLength(0);
segments[3].setLength(0);
}
/**
* Formats a set of arguments to produce a string.
*
* <p>Arguments may appear in the map using named keys (of type String), or
* positional keys (0-based ordinals represented either as type String or
* Integer).
*
* @param argMap A map containing the arguments as (key, value) pairs
* @return Formatted string.
* @throws IllegalArgumentException if the Format cannot format the given
* object
*/
public String format(Map<Object, Object> argMap) {
@Nullable Object[] args = new Object[parameterNames.size()];
for (int i = 0; i < parameterNames.size(); i++) {
args[i] = getArg(argMap, i);
}
return format(args);
}
/**
* Returns the value of the {@code ordinal}th argument.
*
* @param argMap Map of argument values
* @param ordinal Ordinal of argument
* @return Value of argument
*/
private @Nullable Object getArg(Map<Object, Object> argMap, int ordinal) {
// First get by name.
String parameterName = parameterNames.get(ordinal);
Object arg = argMap.get(parameterName);
if (arg != null) {
return arg;
}
// Next by integer ordinal.
arg = argMap.get(ordinal);
if (arg != null) {
return arg;
}
// Next by string ordinal.
return argMap.get(ordinal + "");
}
/**
* Creates a Template with the given pattern and uses it
* to format the given arguments. This is equivalent to
* <blockquote>
* <code>{@link #of(String) Template}(pattern).{@link #format}(args)</code>
* </blockquote>
*
* @throws IllegalArgumentException if the pattern is invalid,
* or if an argument in the
* <code>arguments</code> array is not of the
* type expected by the format element(s)
* that use it.
*/
public static String formatByName(
String pattern,
Map<Object, Object> argMap) {
return Template.of(pattern).format(argMap);
}
/**
* Returns the names of the parameters, in the order that they appeared in
* the template string.
*
* @return List of parameter names
*/
public List<String> getParameterNames() {
return parameterNames;
}
}