Template engine - FreeMarker first experience

Catalog

1、 summary

1.1 Data model

1.2 Common tags for templates

1.3 Template common commands

1.4 Built in functions

2、 Freemarker Basic use of

2.1 Construct the environment

2.2 Write code

2.3 test result

2.4 String template

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1、 summary

FreeMarker It's a template engine ： A template based method 、 Generate text for output ( Anything from HTML Formatted text is used to automatically generate source code ) General tools for .

It is for Java A development package or class library provided by a programmer .

It's not for end users , It's an application for programmers that can be embedded in the products they develop .

For detailed introduction, you can read the introduction on the official website by yourself ： FreeMarker Java Template Engine

FreeMarker Template files mainly include 5 Component composition ：

name	Introduce
Data model	All data that the template can use
Text	The direct output part
notes	namely <#--...--> The format will not output
interpolation （Interpolation）	namely ${..} perhaps #{..} Part of the format , Part of the data model will be used instead of the output
FTL Instructions	FreeMarker Instructions , and HTML The mark is similar to , Add... Before your name # To distinguish , No output .

1.1 Data model

FreeMarker（ And template developers ） Don't care how the data is calculated ,FreeMarker Just know what the real data is .

All the data that the template can use is packaged into data-model Data model .

Detailed introduction ： Template + data-model = output - Apache FreeMarker Manual

1.2 Common tags for templates

stay FreeMarker The template can include the following specific sections ：

label	Introduce
${…}	be called interpolations,FreeMarker The actual value will be substituted in the output .
${name}	You can get root in key by name Of value.
${person.name}	You can get the member variable as person Of name attribute
<#…>	FTL Mark （FreeMarker Template language tags ）： Be similar to HTML Mark , In order to HTML Mark distinction
<@>	macro , Custom tag
notes	Included in <#-- and -->（ instead of ） Between

1.3 Template common commands

1、if Instructions ： Branch control statement .

<#-- if  Instructions  -->
<#if sex=1>
     Gender is male 
    <#elseif sex = 0>
     Gender is female 
    <#else>
     Gender is unknown 
</#if>

2、list、break Instructions ：list Instruction is a typical iterative output instruction , For iterating sets in the output data model .

<#list weeks as w>
    <#if w_has_next> <#-- Whether there is a next object -->
        ,
    </#if>
    <#if w = " Thursday ">
        <#break> <#-- Jump out of iteration -->
    </#if>
    ${w_index} <#-- The index value of the current variable --> =  ${w}
</#list>

3、 include Instructions ：include The function of instructions is similar to JSP Contains instructions for , Used to contain the specified page .

<#include "template01.ftl"> 

 

Write the address of the template directly , because template01.ftl In the same directory as the current template , So you can write the file name directly .

4、 assign Instructions ： It is used to create or replace a top-level variable for the template page

<#assign name = " Everything will always return to plain " />
    ${name}

 

1.4 Built in functions

FreeMarker Some built-in functions are also provided to transform the output , Any variable can be followed by ?,? Followed by the built-in function , You can convert the output variables through built-in functions . Here are the commonly used built-in string functions ：

function	explain
html	html Character escape
cap_first	The first letter of the string becomes uppercase
lower_case	The lowercase form of a string
upper_case	The upper case form of the string
trim	Remove the space at the beginning and end of the string
substring	Truncated string
lenth	Take the length
size	The number of elements in the sequence
int	The integer part of a number （ such as - 1.9?int Namely - 1）

Example

${name?length}

2、 Freemarker Basic use of

2.1 Construct the environment

The first is the construction environment , Let's just build one springBoot project .

The above Apache Freemarker On the hook ,Springboot All help us integrate relevant dependencies .

Then it is to create a folder and src At the same level , It is specially used to put template files .

2.2 Write code

Then go inside and build fremarker file .

Be careful , Suffix is .ftl.

The contents of my documents are those described above .

Then write a test class to test .

 

@Test
void test01() throws Exception {
    //1. establish freeMarker Configure the instance 
    Configuration cfg = new Configuration(Configuration.VERSION_2_3_29);
    //2. Set up the template loader ： Start loading template 
    cfg.setDirectoryForTemplateLoading(new File("templates"));
    //3. Creating a data model 
    Map<String, Object> dataModel = new HashMap<>();
    dataModel.put("username", " Zhang San ");
    dataModel.put("sex", 0);
    
    List<String> weeks = new ArrayList<>();
    weeks.add(" Monday ");
    weeks.add(" Tuesday ");
    weeks.add(" Wednesday ");
    weeks.add(" Thursday ");
    weeks.add(" Friday ");
    dataModel.put("weeks",weeks);
    //4. Access to the template 
    Template template = cfg.getTemplate("template.ftl");
    template.process(dataModel, new PrintWriter(System.out));// Output content in the console 
    template.process(dataModel, new PrintWriter(new File("C:\\Users\\Administrator\\Desktop\\b.txt")));// Output the contents in the file 
    }

2.3 test result

2.4 String template

In one case, we didn't write ftl When you file , You can use it by yourself java Code custom template .

@SpringBootTest
class FreeMarkerApplicationTests {

    private Configuration conf;

    @BeforeEach
    public void init() {
        conf = new Configuration(Configuration.VERSION_2_3_29);
    }
    
    
     @Test
    void test02() throws Exception {
        // 2、 Specify loader  StringTemplateLoader()  String loader 
        conf.setTemplateLoader(new StringTemplateLoader());
        // 3、 Create a string template 
        String templateString = " Welcome ,${username}"; //  String template 
        Template template = new Template("",new StringReader(templateString),conf); //  Create a template from a string 
        //4、 Structural data 
        Map<String,Object> dateModel = new HashMap<>();
        dateModel.put("username"," Li Si ");
        //5、 Processing templates 
        template.process(dateModel, new PrintWriter(new File("C:\\Users\\Administrator\\Desktop\\b.txt")));// Output in file 
    }
    
}

Look at the effect .