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Widened README to 100 columns.

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Not sure why I had it at 80 before, though maybe I'm about to find out when I
push and the formatting is all hosed.
This commit is contained in:
Michael Bayne
2014-03-18 09:29:30 -07:00
parent 9861b54aa0
commit 5ca07f70f0
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README.md
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@@ -1,56 +1,49 @@
This is a Java implementation of the [Mustache template
language](http://mustache.github.com/). There exists [another Java
implementation of Mustache](http://github.com/spullara/mustache.java), but the
motivations for this version are sufficiently different as to justify (in the
author's mind, anyhow) the duplication.
This is a Java implementation of the [Mustache template language](http://mustache.github.com/).
There exists [another Java implementation of Mustache](http://github.com/spullara/mustache.java),
but the motivations for this version are sufficiently different as to justify (in the author's
mind, anyhow) the duplication.
Motivations
===========
* Zero dependencies. You can include this single tiny library in your project
and start making use of templates.
* Usability on a variety of target platforms. The other Java Mustache
implementation requires that a Java compiler be available to compile
templates into Java classes. This implementation makes no such requirements
and as a result is usable on Android, or other exciting places where a Java
compiler is not available. It is even possible to avoid the use of
reflection and provide all of your data as a series of nested Maps, if
desired.
* Zero dependencies. You can include this single tiny library in your project and start making
use of templates.
* Usability on a variety of target platforms. The other Java Mustache implementation requires
that a Java compiler be available to compile templates into Java classes. This implementation
makes no such requirements and as a result is usable on Android, or other exciting places where
a Java compiler is not available. It is even possible to avoid the use of reflection and
provide all of your data as a series of nested Maps, if desired.
* [Proguard](http://proguard.sourceforge.net/) and
[JarJar](http://code.google.com/p/jarjar/) friendly. Though the library
will reflectively access your data (if you desire it), the library makes no
other internal use of reflection or by name instantiation of classes. So
you can embed it using Proguard or JarJar without any annoying surprises.
* [Proguard](http://proguard.sourceforge.net/) and [JarJar](http://code.google.com/p/jarjar/)
friendly. Though the library will reflectively access your data (if you desire it), the library
makes no other internal use of reflection or by name instantiation of classes. So you can embed
it using Proguard or JarJar without any annoying surprises.
* Minimal API footprint. There are really only two methods you need to know
about: `compile` and `execute`. You can even chain them together in cases
where performance is of no consequence.
* Minimal API footprint. There are really only two methods you need to know about: `compile` and
`execute`. You can even chain them together in cases where performance is of no consequence.
Its existence justified by the above motivations, this implementation then
strives to provide additional benefits:
Its existence justified by the above motivations, this implementation then strives to provide
additional benefits:
* It is available via Maven Central, see below for details.
* It is reasonably performant. Templates are parsed separately from
execution. A template will specialize its variables on (class of context,
name) pairs so that if a variable is first resolved to be (for example) a
field of the context object, that will be attempted directly on subsequent
template invocations, and the slower full resolution will only be tried if
accessing the variable as a field fails.
* It is reasonably performant. Templates are parsed separately from execution. A template will
specialize its variables on (class of context, name) pairs so that if a variable is first
resolved to be (for example) a field of the context object, that will be attempted directly on
subsequent template invocations, and the slower full resolution will only be tried if accessing
the variable as a field fails.
Get It
======
JMustache is available via Maven Central and can thus be easily added to your
Maven, Ivy, etc. projects by adding a dependency on
`com.samskivert:jmustache:1.9`. Or download the [pre-built jar
file](http://repo1.maven.org/maven2/com/samskivert/jmustache/1.9/jmustache-1.9.jar).
JMustache is available via Maven Central and can thus be easily added to your Maven, Ivy, etc.
projects by adding a dependency on `com.samskivert:jmustache:1.9`. Or download the
[pre-built jar file](http://repo1.maven.org/maven2/com/samskivert/jmustache/1.9/jmustache-1.9.jar).
Usage
=====
Using JMustache is very simple. Supply your template as a `String` or a
`Reader` and get back a `Template` that you can execute on any context:
Using JMustache is very simple. Supply your template as a `String` or a `Reader` and get back a
`Template` that you can execute on any context:
String text = "One, two, {{three}}. Three sir!";
Template tmpl = Mustache.compiler().compile(text);
@@ -65,8 +58,8 @@ Use `Reader` and `Writer` if you're doing something more serious:
Mustache.compiler().compile(template).execute(data, out);
}
The execution context can be any Java object. Variables will be resolved via
the following mechanisms:
The execution context can be any Java object. Variables will be resolved via the following
mechanisms:
* If the context is a `Map`, `Map.get` will be used.
* If a non-void method with the same name as the variable exists, it will be called.
@@ -96,23 +89,25 @@ Example:
// Elvis: 75
// Madonna: 52
As you can see from the example, the fields (and methods) need not be public.
The `persons` field in the anonymous class created to act as a context is
accessible. Note that the use of non-public fields will not work in a sandboxed
security environment.
As you can see from the example, the fields (and methods) need not be public. The `persons` field
in the anonymous class created to act as a context is accessible. Note that the use of non-public
fields will not work in a sandboxed security environment.
Sections behave as you would expect:
* `Boolean` values enable or disable the section.
* Array, `Iterator`, or `Iterable` values repeatedly execute the section with each element used as the context for each iteration. Empty collections result in zero instances of the section being included in the template.
* An unresolvable or null value is treated as false (by default, see _Default Values_ for more details).
* Array, `Iterator`, or `Iterable` values repeatedly execute the section with each element used as
the context for each iteration. Empty collections result in zero instances of the section being
included in the template.
* An unresolvable or null value is treated as false (by default, see _Default Values_ for more
details).
* Any other object results in a single execution of the section with that object as a context.
See the code in
[MustacheTest.java](http://github.com/samskivert/jmustache/blob/master/src/test/java/com/samskivert/mustache/MustacheTest.java)
for concrete examples. See also the [Mustache
documentation](http://mustache.github.com/mustache.5.html) for details on the
template syntax.
for concrete examples. See also the
[Mustache documentation](http://mustache.github.com/mustache.5.html) for details on the template
syntax.
Partials
--------
@@ -129,16 +124,14 @@ If you wish to make use of partials (e.g. `{{>subtmpl}}`) you must provide a
String tmpl = "...{{>subtmpl}}...";
c.compile(tmpl).execute();
The above snippet will load `new File(templateDir, "subtmpl")` when compiling
the template.
The above snippet will load `new File(templateDir, "subtmpl")` when compiling the template.
Lambdas
-------
JMustache implements lambdas by passing you a `Template.Fragment` instance
which you can use to execute the fragment of the template that was passed to
the lambda. You can decorate the results of the fragment execution, as shown in
the standard Mustache documentation on lambdas:
JMustache implements lambdas by passing you a `Template.Fragment` instance which you can use to
execute the fragment of the template that was passed to the lambda. You can decorate the results of
the fragment execution, as shown in the standard Mustache documentation on lambdas:
String tmpl = "{{#bold}}{{name}} is awesome.{{/bold}}";
Mustache.compiler().compile(tmpl).execute(new Object() {
@@ -154,8 +147,8 @@ the standard Mustache documentation on lambdas:
// result:
<b>Willy is awesome.</b>
You can also obtain the results of the fragment execution to do things like
internationalization or caching:
You can also obtain the results of the fragment execution to do things like internationalization or
caching:
Object ctx = new Object() {
Mustache.Lambda i18n = new Mustache.Lambda() {
@@ -170,16 +163,16 @@ internationalization or caching:
<h2>{{#i18n}}title{{/i18n}</h2>
{{#i18n}}welcome_msg{{/i18n}}
Currently there is no support for "unexecuting" the template and obtaining the
original Mustache template text contained in the section. File a feature
request with a sane use case if you have one.
Currently there is no support for "unexecuting" the template and obtaining the original Mustache
template text contained in the section. File a feature request with a sane use case if you have
one.
Default Values
--------------
By default, an exception will be thrown any time a variable cannot be resolved,
or resolves to null. You can change this behavior in two ways. If you want to
provide a value for use in all such circumstances, use `defaultValue()`:
By default, an exception will be thrown any time a variable cannot be resolved, or resolves to
null. You can change this behavior in two ways. If you want to provide a value for use in all such
circumstances, use `defaultValue()`:
String tmpl = "{{exists}} {{nullValued}} {{doesNotExist}}?";
Mustache.compiler().defaultValue("what").compile(tmpl).execute(new Object() {
@@ -190,9 +183,8 @@ provide a value for use in all such circumstances, use `defaultValue()`:
// result:
Say what what?
If you only wish to provide a default value for variables that resolve to null,
and wish to preserve exceptions in cases where variables cannot be resolved,
use `nullValue()`:
If you only wish to provide a default value for variables that resolve to null, and wish to
preserve exceptions in cases where variables cannot be resolved, use `nullValue()`:
String tmpl = "{{exists}} {{nullValued}} {{doesNotExist}}?";
Mustache.compiler().nullValue("what").compile(tmpl).execute(new Object() {
@@ -202,9 +194,9 @@ use `nullValue()`:
});
// throws MustacheException when executing the template because doesNotExist cannot be resolved
When using a `Map` as a context, `nullValue()` will only be used when the map
contains a mapping to `null`. If the map lacks a mapping for a given variable,
then it is considered unresolvable and throws an exception.
When using a `Map` as a context, `nullValue()` will only be used when the map contains a mapping to
`null`. If the map lacks a mapping for a given variable, then it is considered unresolvable and
throws an exception.
Map<String,String> map = new HashMap<String,String>();
map.put("exists", "Say");
@@ -214,20 +206,18 @@ then it is considered unresolvable and throws an exception.
Mustache.compiler().nullValue("what").compile(tmpl).execute(map);
// throws MustacheException when executing the template because doesNotExist cannot be resolved
Note that section behavior deviates from the above specification (for
historical reasons and because it's kind of useful). By default, a section that
is not resolvable or resolves to null will be omitted (and conversely, an
inverse section that is not resolvable or resolves to null will be included).
If you use `defaultValue()`, this behavior is preserved. If you use
`nullValue()`, sections that refer to an unresolvable variable will now throw
an exception (sections that refer to a resolvable, but null-valued variable,
will behave as before).
Note that section behavior deviates from the above specification (for historical reasons and
because it's kind of useful). By default, a section that is not resolvable or resolves to null will
be omitted (and conversely, an inverse section that is not resolvable or resolves to null will be
included). If you use `defaultValue()`, this behavior is preserved. If you use `nullValue()`,
sections that refer to an unresolvable variable will now throw an exception (sections that refer to
a resolvable, but null-valued variable, will behave as before).
Extensions
==========
JMustache extends the basic Mustache template language with some additional
functionality. These additional features are enumerated below:
JMustache extends the basic Mustache template language with some additional functionality. These
additional features are enumerated below:
Not escaping HTML by default
----------------------------
@@ -280,9 +270,8 @@ Special variables
-----------------
### this
You can use the special variable `this` to refer to the context object itself
instead of one of its members. This is particularly useful when iterating over
lists.
You can use the special variable `this` to refer to the context object itself instead of one of its
members. This is particularly useful when iterating over lists.
Mustache.compiler().compile("{{this}}").execute("hello"); // returns: hello
Mustache.compiler().compile("{{#names}}{{this}}{/names}}").execute(new Object() {
@@ -298,19 +287,17 @@ Note that you can also use the special variable `.` to mean the same thing.
});
// result: TomDickHarry
`.` is apparently supported by other Mustache implementations, though it does
not appear in the official documentation.
`.` is apparently supported by other Mustache implementations, though it does not appear in the
official documentation.
### -first and -last
You can use the special variables `-first` and `-last` to perform special
processing for list elements. `-first` resolves to `true` when inside a section
that is processing the first of a list of elements. It resolves to `false` at
all other times. `-last` resolves to `true` when inside a section that is
processing the last of a list of elements. It resolves to `false` at all other
You can use the special variables `-first` and `-last` to perform special processing for list
elements. `-first` resolves to `true` when inside a section that is processing the first of a list
of elements. It resolves to `false` at all other times. `-last` resolves to `true` when inside a
section that is processing the last of a list of elements. It resolves to `false` at all other
times.
One will often make use of these special variables in an inverted section, as
follows:
One will often make use of these special variables in an inverted section, as follows:
String tmpl = "{{#things}}{{^-first}}, {{/-first}}{{this}}{{/things}}";
Mustache.compiler().compile(tmpl).execute(new Object() {
@@ -318,16 +305,14 @@ follows:
});
// result: one, two, three
Note that the values of `-first` and `-last` refer only to the inner-most
enclosing section. If you are processing a section within a section, there is
no way to find out whether you are in the first or last iteration of an outer
section.
Note that the values of `-first` and `-last` refer only to the inner-most enclosing section. If you
are processing a section within a section, there is no way to find out whether you are in the first
or last iteration of an outer section.
### -index
The `-index` special variable contains 1 for the first iteration through a
section, 2 for the second, 3 for the third and so forth. It contains 0 at all
other times. Note that it also contains 0 for a section that is populated by a
singleton value rather than a list.
The `-index` special variable contains 1 for the first iteration through a section, 2 for the
second, 3 for the third and so forth. It contains 0 at all other times. Note that it also contains
0 for a section that is populated by a singleton value rather than a list.
String tmpl = "My favorite things:\n{{#things}}{{-index}}. {{this}}\n{{/things}}";
Mustache.compiler().compile(tmpl).execute(new Object() {
@@ -342,9 +327,8 @@ singleton value rather than a list.
Compound variables
------------------
In addition to resolving simple variables using the context, you can use
compound variables to extract data from sub-objects of the current context. For
example:
In addition to resolving simple variables using the context, you can use compound variables to
extract data from sub-objects of the current context. For example:
Mustache.compiler().compile("Hello {{field.who}}!").execute(new Object() {
public Object field = new Object() {
@@ -358,22 +342,21 @@ By taking advantage of reflection and bean-property-style lookups, you can do ko
Mustache.compiler().compile("Hello {{class.name}}!").execute(new Object());
// result: Hello java.lang.Object!
Note that compound variables are essentially short-hand for using singleton
sections. The above examples could also be represented as:
Note that compound variables are essentially short-hand for using singleton sections. The above
examples could also be represented as:
Hello {{#field}}{{who}}{{/field}}!
Hello {{#class}}{{name}}{{/class}}!
Note also that one semantic difference exists between nested singleton sections
and compound variables: after resolving the object for the first component of
the compound variable, parent contexts will not be searched when resolving
subcomponents.
Note also that one semantic difference exists between nested singleton sections and compound
variables: after resolving the object for the first component of the compound variable, parent
contexts will not be searched when resolving subcomponents.
Newline trimming
----------------
If the opening or closing section tag are the only thing on a line, any newline
following the tag is trimmed. This allows for civilized templates, like:
If the opening or closing section tag are the only thing on a line, any newline following the tag
is trimmed. This allows for civilized templates, like:
Favorite foods:
{{#people}}
@@ -389,21 +372,20 @@ which produces output like:
rather than:
Favorite foods:
- Elvis Presley likes peanut butter.
- Mahatma Gandhi likes aloo dum.
which would be produced without the newline trimming. Note: the current
implementation does not handle Windows-style CRLF data. If you're a Windows
user, how about sending me a patch?
which would be produced without the newline trimming. Note: the current implementation does not
handle Windows-style CRLF data. If you're a Windows user, how about sending me a patch?
Nested Contexts
---------------
If a variable is not found in a nested context, it is resolved in the next
outer context. This allows usage like the following:
If a variable is not found in a nested context, it is resolved in the next outer context. This
allows usage like the following:
String template = "{{outer}}:\n{{#inner}}{{outer}}.{{this}}\n{{/inner}}";
Mustache.compiler().compile(template).execute(new Object() {
@@ -416,17 +398,15 @@ outer context. This allows usage like the following:
// foo.baz
// foo.bif
Note that if a variable _is_ defined in an inner context, it shadows the same
name in the outer context. There is presently no way to access the variable
from the outer context.
Note that if a variable _is_ defined in an inner context, it shadows the same name in the outer
context. There is presently no way to access the variable from the outer context.
Invertible Lambdas
------------------
For some applications, it may be useful for lambdas to be executed for an
inverse section rather than having the section omitted altogether. This allows
for proper conditional substitution when statically translating templates into
other languages or contexts:
For some applications, it may be useful for lambdas to be executed for an inverse section rather
than having the section omitted altogether. This allows for proper conditional substitution when
statically translating templates into other languages or contexts:
String template = "{{#condition}}result if true{{/condition}}\n" +
"{{^condition}}result if false{{/condition}}";
@@ -460,9 +440,8 @@ InvertibleLambda whenever you need a single function with two modes of operation
Standards Mode
--------------
The more intrusive of these extensions, specifically the searching of parent
contexts and the use of compound varables, can be disabled when creating a
compiler, like so:
The more intrusive of these extensions, specifically the searching of parent contexts and the use
of compound varables, can be disabled when creating a compiler, like so:
Map<String,String> ctx = new HashMap<String,String>();
ctx.put("foo.bar", "baz");
@@ -472,7 +451,7 @@ compiler, like so:
Limitations
===========
In the name of simplicity, some features of Mustache were omitted or
simplified:
In the name of simplicity, some features of Mustache were omitted or simplified:
* `{{= =}}` only supports one or two character delimiters. This is just because I'm lazy and it simplifies the parser.
* `{{= =}}` only supports one or two character delimiters. This is just because I'm lazy and it
simplifies the parser.