//
// JMustache - A Java implementation of the Mustache templating language
// http://github.com/samskivert/jmustache/blob/master/LICENSE
package com.samskivert.mustache;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Represents a compiled template. Templates are executed with a <em>context</em> to generate
* output. The context can be any tree of objects. Variables are resolved against the context.
* Given a name {@code foo}, the following mechanisms are supported for resolving its value
* (and are sought in this order):
* <ul>
* <li>If the variable has the special name {@code this} the context object itself will be
* returned. This is useful when iterating over lists.
* <li>If the object is a {@link Map}, {@link Map#get} will be called with the string {@code foo}
* as the key.
* <li>A method named {@code foo} in the supplied object (with non-void return value).
* <li>A method named {@code getFoo} in the supplied object (with non-void return value).
* <li>A field named {@code foo} in the supplied object.
* </ul>
* <p> The field type, method return type, or map value type should correspond to the desired
* behavior if the resolved name corresponds to a section. {@link Boolean} is used for showing or
* hiding sections without binding a sub-context. Arrays, {@link Iterator} and {@link Iterable}
* implementations are used for sections that repeat, with the context bound to the elements of the
* array, iterator or iterable. Lambdas are current unsupported, though they would be easy enough
* to add if desire exists. See the <a href="http://mustache.github.com/mustache.5.html">Mustache
* documentation</a> for more details on section behavior. </p>
*/
public class Template
{
public static Logger log = LoggerFactory.getLogger(Template.class);
/**
* Executes this template with the given context, writing the results to the supplied writer.
* @throws MustacheException if an error occurs while executing or writing the template.
*/
public void execute (Object context, Writer out) throws MustacheException
{
Context ctx = new Context(context, null, 0, Mode.OTHER);
for (Segment seg : _segs) {
seg.execute(this, ctx, out);
}
}
/**
* Executes this template with the given context, returning the results as a string.
* @throws MustacheException if an error occurs while executing or writing the template.
*/
public String execute (Object context) throws MustacheException
{
StringWriter out = new StringWriter();
execute(context, out);
return out.toString();
}
protected Template (Segment[] segs)
{
_segs = segs;
}
/**
* Called by executing segments to obtain the value of the specified variable in the supplied
* context.
*
* @param ctx the context in which to look up the variable.
* @param name the name of the variable to be resolved, which must be an interned string.
*/
protected Object getValue (Context ctx, String name, int line)
{
// if we're dealing with a compound key, resolve each component and use the result to
// resolve the subsequent component and so forth
if (name.indexOf(".") != -1) {
String[] comps = name.split("\\.");
// we want to allow the first component of a compound key to be located in a parent
// context, but once we're selecting sub-components, they must only be resolved in the
// object that represents that component
Object data = getValue(ctx, comps[0].intern(), line);
for (int ii = 1; ii < comps.length; ii++) {
// generate more helpful error message
if (data == null) {
throw new NullPointerException(
"Null context for compound variable '" + name + "' on line " + line +
". '" + comps[ii - 1] + "' resolved to null.");
}
// once we step into a composite key, we drop the ability to query our parent
// contexts; that would be weird and confusing
data = getValueIn(data, comps[ii].intern(), line);
}
return data;
}
// handle our special variables
if (name == FIRST_NAME) {
return ctx.mode == Mode.FIRST;
} else if (name == LAST_NAME) {
return ctx.mode == Mode.LAST;
} else if (name == INDEX_NAME) {
return ctx.index;
}
while (ctx != null) {
Object value = getValueIn(ctx.data, name, line);
if (value != null) {
return value;
}
ctx = ctx.parent;
}
// Graceful failing, no need to throw exception
log.error("No key, method or field with name '" + name + "' on line " + line);
return new String("{unknown field " + name + "}");
}
protected Object getValueIn (Object data, String name, int line)
{
if (data == null) {
throw new NullPointerException(
"Null context for variable '" + name + "' on line " + line);
}
Key key = new Key(data.getClass(), name);
VariableFetcher fetcher = _fcache.get(key);
if (fetcher != null) {
try {
return fetcher.get(data, name);
} catch (Exception e) {
// zoiks! non-monomorphic call site, update the cache and try again
fetcher = createFetcher(key);
}
} else {
fetcher = createFetcher(key);
}
// if we were unable to create a fetcher, just return null and our caller can either try
// the parent context, or do le freak out
if (fetcher == null) {
return null;
}
try {
Object value = fetcher.get(data, name);
_fcache.put(key, fetcher);
return value;
} catch (Exception e) {
throw new MustacheException(
"Failure fetching variable '" + name + "' on line " + line, e);
}
}
protected final Segment[] _segs;
protected final Map<Key, VariableFetcher> _fcache =
new ConcurrentHashMap<Key, VariableFetcher>();
protected static VariableFetcher createFetcher (Key key)
{
if (key.name == THIS_NAME) {
return THIS_FETCHER;
}
if (Map.class.isAssignableFrom(key.cclass)) {
return MAP_FETCHER;
}
final Method m = getMethod(key.cclass, key.name);
if (m != null) {
return new VariableFetcher() {
public Object get (Object ctx, String name) throws Exception {
return m.invoke(ctx);
}
};
}
final Field f = getField(key.cclass, key.name);
if (f != null) {
return new VariableFetcher() {
public Object get (Object ctx, String name) throws Exception {
return f.get(ctx);
}
};
}
return null;
}
protected static Method getMethod (Class<?> clazz, String name)
{
Method m;
try {
m = clazz.getDeclaredMethod(name);
if (!m.getReturnType().equals(void.class)) {
if (!m.isAccessible()) {
m.setAccessible(true);
}
return m;
}
} catch (Exception e) {
// fall through
}
try {
m = clazz.getDeclaredMethod(
"get" + Character.toUpperCase(name.charAt(0)) + name.substring(1));
if (!m.getReturnType().equals(void.class)) {
if (!m.isAccessible()) {
m.setAccessible(true);
}
return m;
}
} catch (Exception e) {
// fall through
}
Class<?> sclass = clazz.getSuperclass();
if (sclass != Object.class && sclass != null) {
return getMethod(clazz.getSuperclass(), name);
}
return null;
}
protected static Field getField (Class<?> clazz, String name)
{
Field f;
try {
f = clazz.getDeclaredField(name);
if (!f.isAccessible()) {
f.setAccessible(true);
}
return f;
} catch (Exception e) {
// fall through
}
Class<?> sclass = clazz.getSuperclass();
if (sclass != Object.class && sclass != null) {
return getField(clazz.getSuperclass(), name);
}
return null;
}
protected static enum Mode { FIRST, OTHER, LAST };
protected static class Context
{
public final Object data;
public final Context parent;
public final int index;
public final Mode mode;
public Context (Object data, Context parent, int index, Mode mode) {
this.data = data;
this.parent = parent;
this.index = index;
this.mode = mode;
}
public Context nest (Object data, int index, Mode mode) {
return new Context(data, this, index, mode);
}
}
/** A template is broken into segments. */
protected static abstract class Segment
{
abstract void execute (Template tmpl, Context ctx, Writer out);
protected static void write (Writer out, String data) {
try {
out.write(data);
} catch (IOException ioe) {
throw new MustacheException(ioe);
}
}
}
/** Used to cache variable fetchers for a given context class, name combination. */
protected static class Key
{
public final Class<?> cclass;
public final String name;
public Key (Class<?> cclass, String name) {
this.cclass = cclass;
this.name = name;
}
@Override public int hashCode () {
return cclass.hashCode() * 31 + name.hashCode();
}
@Override public boolean equals (Object other) {
Key okey = (Key)other;
return okey.cclass == cclass && okey.name == name;
}
}
protected static abstract class VariableFetcher {
abstract Object get (Object ctx, String name) throws Exception;
}
protected static final VariableFetcher MAP_FETCHER = new VariableFetcher() {
public Object get (Object ctx, String name) throws Exception {
return ((Map<?,?>)ctx).get(name);
}
};
protected static final VariableFetcher THIS_FETCHER = new VariableFetcher() {
public Object get (Object ctx, String name) throws Exception {
return ctx;
}
};
protected static final String THIS_NAME = "this".intern();
protected static final String FIRST_NAME = "-first".intern();
protected static final String LAST_NAME = "-last".intern();
protected static final String INDEX_NAME = "-index".intern();
}