Define directives
Basics
A macro is a template fragment associated with a variable.
<#macro gray>
<span class="text-muted">Hello Joe!</span>
</#macro>
The macro directive itself does not print anything;
You use user-defined directives by writing @ instead of # in the FTL tag. Use the variable name as the directive name.
<@macro gray></@macro>
or
<@macro/>
- output
<span class="text-muted">Hello Joe!</span>
Parameters
Let’s improve the gray macro so it can use arbitrary name, not only Joe. For this purpose you can use parameters.
- define & called
<#macro gray name>
<span class="text-muted">Hello ${name}!</span>
</#macro>
<@gray name="echo">
- output
<span class="text-muted">Hello echo!</span>
You can use multiple parameters, like
- define & called
<#macro gray name size>
<span class="text-muted" size="${size}">Hello ${name}!</span>
</#macro>
<@gray name="echo" size=14 />
- output
<span class="text-muted" size="14">Hello echo!</span>
You can give method a default value, such as
- define & called
<#macro gray name size=14>
<span class="text-muted" size="${size}">Hello ${name}!</span>
</#macro>
<@gray name="echo" />
- output
<span class="text-muted" size="14">Hello echo!</span>
Nested content
Custom directive can have nested content, similarly as predefined directives like
<#if ...>nested content</#if>
can have.
- define & called
<#macro border>
<div class="warp">
<#nested>
</div>
</#macro>
<@border>Here is the nested content.</@border>
- output
<div class="warp">
Here is the nested content.
</div>
The nested directive can be called for multiple times, for example:
- define & called
<#macro do_three>
<div class="warp">
<#nested>
<#nested>
<#nested>
</div>
</#macro>
<@do_three>hello world</@do_three>
- output
<div class="warp">
Hello world
Hello world
Hello world
</div>
The local variables of a macro are not visible in the nested content. Say, this:
- define & called
<#macro repeat count>
<#local y = "test">
<#list 1..count as x>
${y} ${count}/${x}: <#nested>
</#list>
</#macro>
<@repeat count=3>${y!"?"} ${x!"?"} ${count!"?"}</@repeat>
- output
test 3/1: ? ? ?
test 3/2: ? ? ?
test 3/3: ? ? ?
Macros with loop variables
User-defined directives can also have loop variables.
- define & called
<#macro do_three>
<#nested 1>
<#nested 2>
<#nested 3>
</#macro>
<@do_three ; x> <#-- user-defined directive uses ";" instead of "as" -->
${x} Anything.
</@do_three>
- output
1 Anything.
2 Anything.
3 Anything.
The name of the loop variable is specified in the user-defined directive open tag (<@…>) after the parameters and a semicolon.
- define & called
<#macro repeat count>
<#list 1..count as x>
<#nested x, x/2, x==count>
</#list>
</#macro>
<@repeat count=4 ; c, halfc, last>
${c}. ${halfc}<#if last> Last!</#if>
</@repeat>
- output
1. 0.5
2. 1
3. 1.5
4. 2 Last!
Define variables
Create and replace variables with assign
- define
<#assign name = "echo"> <#-- create variable echo -->
${name}
<#assign name = "hello"> <#-- replace variable name -->
${name}
- output
echo
hello
Local variables hide (not overwrite) plain variables of the same name.
Loop variables hide (not overwrite) local and plain variables of the same name.
For example:
<#assign x = "plain">
1. ${x} <#-- we see the plain var. here -->
<@test/>
6. ${x} <#-- the value of plain var. was not changed -->
<#list ["loop"] as x>
7. ${x} <#-- now the loop var. hides the plain var. -->
<#assign x = "plain2"> <#-- replace the plain var, hiding does not mater here -->
8. ${x} <#-- it still hides the plain var. -->
</#list>
9. ${x} <#-- the new value of plain var. -->
<#macro test>
2. ${x} <#-- we still see the plain var. here -->
<#local x = "local">
3. ${x} <#-- now the local var. hides it -->
<#list ["loop"] as x>
4. ${x} <#-- now the loop var. hides the local var. -->
</#list>
5. ${x} <#-- now we see the local var. again -->
</#macro>
- output
1. plain
2. plain
3. local
4. loop
5. local
6. plain
7. loop
8. loop
9. plain2
Namespaces
Creating a library
- +add file lib.ftl
<#assign mail = "[email protected]">
<#macro copyright date name="Echo">
Copyright (C) ${date} ${name}. All rights reserved.
</#macro>
- define ftl
<#import "lib.ftl" as my> <#-- the hash called "my" will be the "gate" -->
<@my.copyright date="1994-2016"/>
${my.mail}
<#assign mail="[email protected]">
${mail}
- output
Copyright (C) 1994-2016 Echo. All rights reserved.
[email protected]
[email protected]
Writing the variables of imported namespaces
Occasionally you may want to create or replace a variable in an imported namespace.
You can do this with the assign directive, if you use its namespace parameter. For example:
- define
<#import "lib.ftl" as my> <#-- the hash called "my" will be the "gate" -->
${my.mail}
<#assign mail="[email protected]" in my>
${my.mail}
- output
Namespaces and data-model
- lib.ftl
<#macro copyright date name="${name}">
Copyright (C) ${date} ${name}. All rights reserved.
</#macro>
<#assign mail = "houbb.${name}@gmail.com">
- demo.ftl
<#import "lib.ftl" as my> <#-- the hash called "my" will be the "gate" -->
<@my.copyright date="1994-2016" />
${my.mail}
- data-model
public class Demo {
public static void main(String[] args) throws Exception {
Template template = FreemarkerHelper.getTemplate("demo.ftl");
//map build
Map<String, Object> map = new HashMap<String, Object>();
map.put("name", "echo");
FileHelper.createFile(template, "demo.html", map);
}
}
- output
Copyright (C) 1994-2016 echo. All rights reserved.
[email protected]
Life-cycle of namespaces
If you try to import with the same path for multiple times, it will create the namespace and run the template specified
by the path for the very first invocation of import only. The later imports with the same path will just
create a gate hash to the same namespace. For example:
- ftl
<#import "lib.ftl" as my> <#-- the hash called "my" will be the "gate" -->
<#import "lib.ftl" as foo> <#-- the hash called "foo" will be the "gate" -->
<#import "lib.ftl" as bar> <#-- the hash called "bar" will be the "gate" -->
${my.mail}
${foo.mail}
${bar.mail}
<#assign mail="[email protected]" in my>
${my.mail}
${foo.mail}
${bar.mail}
- output
Extends
Now, we extends freemarker, add three directive :
@extends,@block,@override
Parent template define the layout, child template can override the content of layout.
- +add base.ftl
<html>
<head>
<@block name="head">base_head_content</@block>
</head>
<body>
<@block name="body">base_body_content</@block>
</body>
</html>
- change demo.ftl
<@override name="body">
<div class='content'>
Powered By rapid-framework
</div>
</@override>
<@extends name="base.ftl"/>
- output
<html>
<head>
base_head_content
</head>
<body>
<div class='content'>
Powered By rapid-framework
</div>
</body>
</html>
- Before use these extends directive, you should add them into config.
/**
* define Configuration
* @return
* @throws Exception
*/
public static Configuration getConfiguration() throws Exception {
if(configuration == null) {
configuration = new Configuration();
configuration.setDirectoryForTemplateLoading(new File(PathHelper.getWebPath())); //path
configuration.setObjectWrapper(new DefaultObjectWrapper());
configuration.setSharedVariable("block", new BlockDirective());
configuration.setSharedVariable("override", new OverrideDirective());
configuration.setSharedVariable("extends", new ExtendsDirective());
}
return configuration;
}
these directives belong to rapid-framework.
Or, you can also just following files into your project.In fact, it’s part of rapid-framework.jar
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