ftl assign map

Using FreeMarker templates (FTL)- Tutorial

1. introduction to freemarker, 2. installation of freemarker, 3. eclipse integration, 4. basic example, 5.1. reuse common template fragments, 5.2. variables, 5.3. if then else, 5.4. handling null/undefined values, 5.5. escape, 6.1. freemarker homepage.

FreeMarker Tutorial. This tutorial explains how can you define FreeMarker templates and how can you generate output based on these templates. It also demonstrates the usage of macros.

FreeMarker is a Java-based template engine which can be used in stand-alone or servlet-based Java programs.

In FreeMarker you define templates, which are text files that contain the desired output, except that they contain placeholders like ${name} , and even some logic like conditionals, loops, etc. In your Java program you supply the actual values for these placeholders and the final output is generated based on this input.

The input of templates is a bunch of named variables that you usually provide as a Map<String, Object> (the Map entries will be the variables) or as a JavaBean (the JavaBean properties will be the variables). The variable values can be simple strings, numbers and such primitive values, but also lists, maps, or arbitrary Java objects whose methods you can call from the template. Note that when accessing JavaBean properties, myObject.myProperty syntax should be used instead of myObject.getMyProperty() .

The output of templates is written into a Writer that you provide, so it can go into a HTTP response (for dynamic web pages), into a local file, into a String , etc.

It is configurable from where FreeMarker reads the templates; commonly used options are loading from a file-system directory, from the class-path, from the servlet context ( WEB-INF/templates or such), or even from a database table. It’s also possible to "load" templates directly from String objects.

To use FreeMarker download the latest version of it from the following webpage and add it to the classpath of your Java project.

FreeMarker code completion and syntax highlighting is part of the JBoss Tools . Add the following update site to your Eclipse installation via Help   Install New Software…​

Create a new Java project called com.vogella.freemarker.first . Create a new folder called lib and add the Freemarker library to it. Add this library to the classpath for your project.

If you don’t know how to achieve that, please see the Eclipse IDE Tutorial for instructions on the required steps.

Create a new folder called templates inside the folder of the com.vogella.freemarker.first package. Inside that, create the following file with name helloworld.ftl .

Create the following class which demonstrates the usage of Java objects in templates.

Create the following class which creates the input for this template and creates the output.

5. Useful FTL tricks

When you find yourself copy-pasting common parts between templates a lot, you should probably use macros.

Continuing our last example, create a new folder called lib inside the templates directory, and there create a file called utils.ftl , with this content:

Now you can simplify helloworld.ftl like this:

Another way of reusing template fragments is moving the common fragment into its own ftl file. Then just insert it with <#include "lib/myfragment.ftl"> . This is less flexible than macros, but simpler in concept: it mimics copy-pasting.

You can define and assign content to variables inside the FTL files for easy reuse.

` You can handle if / else cases, see below for an example.

FreeMarker requires you to provide an explicit default for variables, so avoid values that are null or undefined:

When generating HTML, it’s important to escape < , & , etc. in values that were not meant to store HTML and can contain these problematic characters. You can apply such escaping like ${message?html} . You can also ask FreeMarker to add ?html to all ${} -s in a section like this:

It’s important to understand that #escape only affects the ${} bits that are inside the enclosed section in the template file when you look at it in a text editor. That means, ${} embracements which are in other templates or macros called from there, won’t be affected.

6. Links and Literature

FreeMarker homepage

If you need more assistance we offer Online Training and Onsite training as well as consulting

See License for license information .

• Documentation
• GeoServer 2.25.x User Manual »
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• Freemarker Templates

Freemarker Templates ¶

Introduction ¶.

This tutorial will introduce you to a more in depth view of what FreeMarker templates are and how you can use the data provided to templates by GeoServer.

Freemarker is a simple yet powerful template engine that GeoServer uses to allow user customization of outputs. In particular, at the time of writing it’s used to allow customization of GetFeatureInfo, GeoRSS and KML outputs.

Freemarker allows for simple variable expansions, as in ${myVarName} , expansion of nested properties, such as in ${feature.myAtt.value} , up to little programs using loops, ifs and variables. Most of the relevant information about how to approach template writing is included in the Freemarker’s Designer guide and won’t be repeated here: the guide, along with the KML Placemark Templates and GetFeatureInfo Templates tutorials should be good enough to give you a good grip on how a template is built.

Template Lookup ¶

GeoServer looks up templates in three different places, allowing for various levels of customization. For example given the content.ftl template used to generate WMS GetFeatureInfo content:

Look into GEOSERVER_DATA_DIR/workspaces/<workspace>/<datastore>/<featuretype>/content.ftl to see if there is a feature type specific template

Look into GEOSERVER_DATA_DIR/workspaces/<workspace>/<datastore>/content.ftl to see if there is a store specific template

Look into GEOSERVER_DATA_DIR/workspaces/<workspace>/content.ftl to see if there is a workspace specific template

Look into GEOSERVER_DATA_DIR/workspaces/content.ftl looking for a global override

Look into GEOSERVER_DATA_DIR/templates/content.ftl looking for a global override

Look into the GeoServer classpath and load the default template

Each templated output format tutorial should provide you with the template names, and state whether the templates can be type specific, or not. If you can’t find the source files for the default template, look in the service jar of the geoserver distribution (for example, wms-x.y.z.jar). You just have to unzip it, and you’ll find the xxx.ftl files GeoServer is using as the default templates.

Common Data Models ¶

Freemarker calls “data model” the set of data provided to the template. Each output format used by GeoServer will inject a different data model according to the information it’s managing. There are three very common elements that appear in almost every template: Feature, FeatureType and FeatureCollection. Here we provide a data model of each.

The data model is a sort of tree, where each element has a name and a type. Besides basic types, we’ll use:

list: a flat list of items that you can scan thru using the FreeMarker <#list> directive;

map: a key/value map, that you usually access using the dot notation, as in ${myMap.myKey }, and can be nested;

listMap: a special construct that is, at the same time, a Map, and a list of the values.

Here are the data models (as you can see there are redundancies, in particular in attributes, we chose this approach to make template building easier):

FeatureType (map)

name (string): the type name

attributes (listMap): the type attributes

name (string): attribute name

namespace (string): attribute namespace URI

prefix (string): attribute namespace prefix

type (string): attribute type, the fully qualified Java class name

isGeometry (boolean): true if the attribute is geometric, false otherwise

Feature (map)

fid (string): the feature ID (WFS feature id)

typeName (string): the type name

attributes (listMap): the list of attributes (both data and metadata)

value: a string representation of the attribute value

isComplex (boolean): true if the attribute is a feature (see Complex Features ), false otherwise

type (string or FeatureType): attribute type: if isComplex is false, the fully qualified Java class name; if isComplex is true, a FeatureType

rawValue: the actual attribute value (is isComplex is true rawValue is a Feature)

name (string): the type name (same as typeName)

title (string): The title configured in the admin console

abstract (string): The abstract for the type

description (string): The description for the type

keywords (list): The keywords for the type

metadataLinks (list): The metadata URLs for the type

SRS (string): The layer’s SRS

nativeCRS (string): The layer’s coordinate reference system as WKT

FeatureCollection (map)

features (list of Feature, see above)

type (FeatureType, see above)

request (map)

Contains the GetFeatureInfo request parameters and related values.

environment (map)

Allows accessing several environment variables, in particular those defined in:

JVM system properties OS environment variables web.xml context parameters

Allows accessing math functions.

${request.LAYERS} ${request.ENV.PROPERTY}

environment

${environment.GEOSERVER_DATA_DIR} ${environment.WEB_SITE_URL}

${Math.max(request.NUMBER1,request.NUMBER2)}

Table Of Contents

• Template Lookup
• Common Data Models

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• FreeMarker 中文官方参考手册
• Alpha. index
• Expressions
• #directives
• name ：变量的名字。 它不是表达式。而它可以写作是字符串，如果变量名包含保留字符这是很有用的， 比如 <#assign "foo-bar" = 1> 。 请注意这个字符串没有展开插值(如 "${foo}" )； 如果需要赋值一个动态创建的名字，那么不得不使用 这个技巧 。
• = ：赋值操作符。 它也可以是一个简写的赋值操作符(从 FreeMarker 2.3.23 版本开始)： ++ ， -- ， += ， -= ， *= ， /= 或 %= 。比如 <#assign x++> 和 <#assign x = x + 1> 是一样的，并且 <#assign x += 2> 和 <#assign x = x + 2> 是相同的。 请注意， ++ 通常意味着算术加法 (对于非数字将会失败)，不像 + 或 += 可以进行字符连接等重载操作。
• value ： 存储的值。是表达式。
• namespacehash ：(通过 import ) 为命名空间创建的哈希表。是表达式。

使用该指令你可以创建一个新的变量， 或者替换一个已经存在的变量。注意仅仅顶级变量可以被创建/替换 (也就是说你不能创建/替换 some_hash.subvar ， 除了 some_hash )。

关于变量的更多内容，请阅读： 模板开发指南/其它/在模板中定义变量

比如：变量 seq 存储一个序列：

比如：变量 x 中存储增长的数字：

作为一个方便的特性，你可以使用一个 assign 标记来进行多次定义。比如这个会做上面两个例子中相同的事情：

如果你知道什么是命名空间： assign 指令在命名空间中创建变量。通常它在当前的命名空间 (也就是和标签所在模板关联的命名空间)中创建变量。但如果你是用了 in namespacehash ， 那么你可以用另外一个 命名空间 来创建/替换变量。 比如，这里你在命名空间中 /mylib.ftl 创建/替换了变量 bgColor ：

assign 的极端使用是当它捕捉它的开始标记和结束标记中间生成的输出时。 也就是说，在标记之间打印的东西将不会在页面上显示， 但是会存储在变量中。比如：

请注意，你不应该使用它来往字符串中插入变量：

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Generated for: Freemarker 2.3.23 Last generated: 2015-09-18 14:38:51 GMT

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ViralPatel.net

How To Iterate HashMap in FreeMarker (FTL)

by Viral Patel · May 2, 2012

In this short article we will see how to iterate an HashMap in FreeMarker template. Consider below code which is normally used to iterate a List in FTL.

Here in above code, we created a List object and passed it to FTL page. In FTL we used <#list> to iterate and print its values.

Problem Statement

So here’s the problem statement. I have an Hashmap which I want to iterate and display in my FTL (FreeMarker) template. Consider following code in Java. So how to iterate this Hashmap in FTL and display its values?

Well, the above hashmap can be iterated in FTL using following code:

In above code, we used ?keys attribute to get the keySet of HashMap . This key set is iterated and corresponding value is fetched by user.get(key) method. Note: One thing that’s worth noting here is that the sequence in which the values are printing may be different then the actual sequence in which values are added in hashmap. This is because, hashmap doesn’t preserve order or values. If you want to preserve the sequence of keys use LinkedHashMap .

Hope this helps.

Tags: Freemarker FTL java code

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10 comments.

Nice one, exactly what I was looking for! Thanks for the post!

How do i access the next element in a sequence in freemarker

I have tried this but doesnt work

How do I iterate over a hashmap<String,List> in freemarker? abc() takes as input only strings or arrays. Not lists & the hashmap which I am looking at contains Keys as String & Value as a list of strings. I want the output to be like :

A= apple,mango,banana B = x,e,t,

abc().setTargeting(‘${key?js_string}’,’${key_value_list_map[key]}’);

Nice Article. But when I try this:

${key} = ${criteriaMap[key]}

It throws exception: freemarker.core.InvalidReferenceException: Expression criteriaMap[key] is undefined.

However, If i print key only using ${key} , the code works. I dont know why “criteriaMap[key]” is causing trouble.

Thanks in advance

PS: There is a Line in your article “corresponding value is fetched by user.get(key) method.” where is user in the article, its confusing.

Staring from FreeMarker 2.3.25 you can do this: ${key} = ${value}

My last comment was mangled… so again, staring from FreeMarker 2.3.25 you can do this:

${key} = ${value}

I have no idea what the syntax of the comments is… a last attempt:

Hi, I’m unable to get the desired output and getting following error: FreeMarker template error: The following has evaluated to null or missing: ==> key [in template “template/xyz.ftl” at line 35, column 19]

Code Snippet:

FROM HERE [#if sourceList?? && sourceList?has_content] Source: ${sourceList}

${key} = ${value};

[#else] sourceList is empty [/#if] TILL HERE

Output (after commenting out [#– ${key} = ${value}; –]) FROM HERE

Source: {a12=Test} List:

TILL HERE Would appreciate all the help.

when I iterate , I am getting unnecessary key and values like,size, clone, equals etc.. how to avoid those values.

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• Report a Bug
• Apache FreeMarker Manual
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Built-ins for hashes

• Alpha. index
• Expressions
• #directives

A sequence that contains all the lookup keys in the hash.

Note that not all hashes support this (ask the programmer if a certain hash allows this or not).

Since hashes do not define an order for their sub variables in general, the order in which key names are returned can be arbitrary. However, some hashes maintain a meaningful order (ask the programmer if a certain hash does that or not). For example, hashes created with the above { ... } syntax preserve the same order as you have specified the sub variables.

To list both the keys and the values, you can use <#list attrs as key, value>...<#list> ; see the list directive .

A sequence that contains all the variables (the values in the key-value pairs) in the hash.

As of the order in which the values are returned, the same applies as with the keys built-in; see there. Furthermore, it's not guaranteed that the order of the values corresponds to the order of the keys returned by the keys build-in.

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Last generated: 2024-02-12 20:34:04 GMT , for Freemarker 2.3.32

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