当前位置：网站首页>[template engine] microservice Learning Notes 6: freemaker

[template engine] microservice Learning Notes 6: freemaker

2022-07-25 03:16:00 【Driver Zhao Si】

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Preface ：

1. Based on Springboot The single project introduction of has been completed , As for the realization of other functions in the project, I'm not going to introduce them here , Because the knowledge involved is not difficult , And they are all simple CRUD operation , If you are interested, you can send me a private message. I'll see if I want to write a few articles to introduce .
2. Complete the previous stage of learning , I put myself into the study of microservices , The tutorials used are B The microservice tutorial of dark horse on the website . Because my memory is not very good , So for the study of new things, I prefer to take notes to enhance understanding , Here I will summarize the key contents of my notes and post them to “ Micro service learning ” In the notes column . I'm Zhao Si , A programmer with pursuit , I hope you can support me a lot , It would be better if you could give me some attention .

Catalog

One ：🧸freemarker brief introduction

Two ：🧸 Environment building

1.🧩 Create a project & Introduce dependencies

2.🧩 Add configuration file

3、 ... and ：🧸 Template testing

1.🧩 Create an entity class to test

2.🧩 Create a template

3.🧩 establish Controller

4.🧩 Create startup class

5.🧩 To test

Four ：🧸Freemarker Common grammar

1：🧩 Basic grammar types

2：🧩 Set instruction (Map and List)

2.1： Create the corresponding controller

2.2： Template implementation

2.3： test

3.🧩if Instructions

4.🧩 Operator

4.1： Arithmetic operator

4.2： Comparison operator

4.3： Logical operators

5.🧩 Null processing

5.1： Determine whether a variable is used “??”

5.2： The default value of the missing variable is “!”

6.🧩 Built-in functions

6.1： And the size of a collection

6.2： Date formatting

6.3： Built-in functions c

6.4： take json String to object

7.🧩 Static testing

7.1： modify application.yml file

7.2： stay test Create a test class

7.3： Result display

One ：🧸freemarker brief introduction

FreeMarker Is a template engine ： It's based on the template and the data to be changed , And used to generate output text (HTML Webpage , E-mail , The configuration file , Source code, etc ) General tools for . It's not for end users , It is a Java Class library , It's a component that programmers can embed in their products .

The template is written as FreeMarker Template Language (FTL). It's simple , Special language , It's not like PHP That mature programming language . That means preparing data for display in real programming languages , For example, database query and business operation , After that, the template shows the prepared data . In the template , You can focus on how to present data , Outside of the template, you can focus on what data to show .

frequently-used java The template has jsp、Velocity、thmeleaf、freemarker etc. , The difference between them is as follows ：

1.Jsp by Servlet special , Cannot be used alone .

2.Thymeleaf For new technology , More powerful , But the efficiency of implementation is relatively low .

3.Velocity from 2010 Updated in 2.0 After version , There is no update .Spring Boot The official in the 1.4 This is no longer supported after version , although Velocity stay 2017 The year version is iterated , But it's too late .

4.Freemarker Good performance , Is a powerful and lightweight template language .

Two ：🧸 Environment building

1.🧩 Create a project & Introduce dependencies

<dependencies>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-freemarker</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
</dependency>
<!-- lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

<!-- apache  Yes  java io  Package tool library  -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-io</artifactId>
    <version>1.3.2</version>
</dependency>
</dependencies>

2.🧩 Add configuration file

server:
  port: 8881 # Service port 
spring:
  application:
    name: freemarker-demo # Specify the service name 
  freemarker:
    cache: false  # Turn off template caching , Convenient test 
    settings:
      template_update_delay: 0 # Check the template update delay time , Set to 0 Means to check immediately , If the time is longer than 0 There will be caches that are not convenient for template testing 
    suffix: .ftl               # Appoint Freemarker The suffix of the template file

3、 ... and ：🧸 Template testing

1.🧩 Create an entity class to test

package com.my.freemarker.entity;

import lombok.Data;

import java.util.Date;

@Data
public class Student {
    private String name;
    private int age;
    private Date birthday;
    private Float money;
}

2.🧩 Create a template

stay resources Create templates, This directory is freemarker The default template storage directory .

stay templates Create a template file under 01-basic.ftl , The interpolation expression in the template will eventually be freemarker Replace with specific data .

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Hello World!</title>
</head>
<body>
<b> Plain text  String  Exhibition ：</b><br><br>
Hello ${name} <br>
<hr>
<b> object Student Data presentation in ：</b><br/>
 full name ：${stu.name}<br/>
 Age ：${stu.age}
<hr>
</body>
</html>

3.🧩 establish Controller

package com.my.freemarker.controller;

import com.my.freemarker.entity.Student;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class helloController {
    @GetMapping("/basic")
    public String helloTest(Model model){
        //1. Plain text formal parameters 
        model.addAttribute("name","freemarker");
        //2. Entity class related parameters 
        Student stu = new Student();
        stu.setName(" Xiao Ming ");
        stu.setAge(19);
        stu.setMoney(100F);
        model.addAttribute("stu",stu);

        return "01-basic";
    }
}

4.🧩 Create startup class

package com.my.freemarker;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class FreemarkerApplication {
    public static void main(String[] args) {
        SpringApplication.run(FreemarkerApplication.class,args);
    }
}

5.🧩 To test

Browser input http:localhost:8881/basic

You can see that the data is successfully displayed .

Four ：🧸Freemarker Common grammar

1：🧩 Basic grammar types

1. notes , namely <#-- Content -->, The content between them will be freemarker Treat as comments

2. interpolation (interpolation)： namely ${..} part ,freeremarker Will replace... With real values ${..}

3.FTL Instructions ： and HTML The mark is similar to , Add... Before your name # To distinguish ,Freeremarker Will parse expressions or logic in tags

<# > FTL Instructions  </#>

4. Text , Enter text information , These are not freeremarker Notes 、 interpolation 、FTL The content of the instruction will be freeremarker Ignore parsing , Output its contents directly .

2：🧩 Set instruction (Map and List)

2.1： Create the corresponding controller

@GetMapping("/list")
public String list(Model model){
    //------------------------------------
    Student stu1 = new Student();
    stu1.setName(" cockroach ");
    stu1.setAge(18);
    stu1.setMoney(1000.86f);
    stu1.setBirthday(new Date());

    // Little red object model data 
    Student stu2 = new Student();
    stu2.setName(" Xiaohong ");
    stu2.setMoney(200.1f);
    stu2.setAge(19);

    // Store the data of two object models in List Collection 
    List<Student> stus = new ArrayList<>();
    stus.add(stu1);
    stus.add(stu2);

    // towards model In the store List Aggregate data 
    model.addAttribute("stus",stus);

    //------------------------------------
    // establish Map data 
    HashMap<String,Student> stuMap = new HashMap<>();
    stuMap.put("stu1",stu1);
    stuMap.put("stu2",stu2);
    
    // 3.1  towards model In the store Map data 
    model.addAttribute("stuMap", stuMap);
    return "02-list";
}

2.2： Template implementation

stay templates Add... To the package "02-list.ftl"

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Hello World!</title>
</head>
<body>

<#-- list  Data display  -->
<b> Exhibition list Medium stu data :</b>
<br>
<br>
<table>
    <tr>
        <td> Serial number </td>
        <td> full name </td>
        <td> Age </td>
        <td> wallet </td>
    </tr>
    <#list stus as stu>
        <tr>
            <td>${stu_index+1}</td>   <!-- index： Get the subscript of the loop , The method of use is in stu Add after "_index", Its value is from 0 Start  -->
            <td>${stu.name}</td>
            <td>${stu.age}</td>
            <td>${stu.money}</td>
        </tr>
    </#list>

</table>
<hr>

<#-- Map  Data display  -->
<b>map Data display ：</b>
<br/><br/>
<a href="###"> Mode one ： adopt map['keyname'].property</a><br/>
 Output stu1 Student information ：<br/>
 full name ：${stuMap['stu1'].name}<br/>
 Age ：${stuMap['stu1'].age}<br/>
<br/>
<a href="###"> Mode two ： adopt map.keyname.property</a><br/>
 Output stu2 Student information ：<br/>
 full name ：${stuMap.stu2.name}<br/>
 Age ：${stuMap.stu2.age}<br/>

<br/>
<a href="###"> Traverse map Two student information ：</a><br/>
<table>
    <tr>
        <td> Serial number </td>
        <td> full name </td>
        <td> Age </td>
        <td> wallet </td>
    </tr>
    <#list stuMap?keys as key >
        <tr>
            <td>${key_index}</td>
            <td>${stuMap[key].name}</td>
            <td>${stuMap[key].age}</td>
            <td>${stuMap[key].money}</td>
        </tr>
    </#list>
</table>
<hr>

</body>
</html>

2.3： test

Type in the browser address bar http:localhost:8881/list

You can see that the data is successfully displayed

3.🧩if Instructions

if An instruction is a judgment instruction , It is commonly used. FTL Instructions ,freemarker Encountered while parsing if They make judgments , If the condition is true, output if In the middle , Otherwise, skip the content and no longer output .

<#if ></if>

Use list The data in the instruction is used as the data model , Name it “ Xiaohong ” The data output of is red

<#list stus as stu>
    <#if stu.name = ' Xiaohong '>
        <tr style="color: red">
            <td>${stu_index+1}</td>   <!-- index： Get the subscript of the loop , The method of use is in stu Add after "_index", Its value is from 0 Start  -->
            <td>${stu.name}</td>
            <td>${stu.age}</td>
            <td>${stu.money}</td>
        </tr>
        <#else >
            <tr>
                <td>${stu_index+1}</td>
                <td>${stu.name}</td>
                <td>${stu.age}</td>
                <td>${stu.money}</td>
            </tr>
    </#if>
</#list>

You can see that success “ Xiaohong ” Turn red .

4.🧩 Operator

4.1： Arithmetic operator

FreeMarker Expression supports +、-、*、/、% operation , Just put the operation expression into ${} Then you can .

4.2： Comparison operator

= perhaps ==: Determine if two values are equal .
!=: Judge whether the two values are not equal .
> perhaps gt: Judge whether the left value is greater than the right value
>= perhaps gte: Judge whether the left value is greater than or equal to the right value
< perhaps lt: Determine whether the left value is less than the right value
<= perhaps lte: Judge whether the left value is less than or equal to the right value

4.3： Logical operators

Logic and :&&
Logic or :||
Logic is not :!

Logical operators can only work on Boolean values , Otherwise there will be a mistake .

5.🧩 Null processing

5.1： Determine whether a variable is used “??”

Usage for :variable??, If the variable exists , return true, Otherwise return to false

example ： To prevent stus If it is empty, you can add the following judgment ：

<#if stus??>
<#list stus as stu>
     ......
</#list>
</#if>

5.2： The default value of the missing variable is “!”

Use ! To specify a default value , Display the default value when the variable is empty
example ： ${name!''} Said if name Displays an empty string if it is empty .
If it is a nested object, it is recommended to use （） Cover up
example ： ${(stu.bestFriend.name)!''} Express , If stu or bestFriend or name If it is empty, the empty string will be displayed by default .

6.🧩 Built-in functions

Built in function syntax format ： Variable +?+ The name of the function

6.1： And the size of a collection

${ Collection name ?size}

6.2： Date formatting

Show the year, month and day : ${today?date} Display minutes and seconds ：${today?time} Show date + Time ：${today?datetime} Custom formatting ： ${today?string("yyyy year MM month ")}

6.3： Built-in functions `c`

model.addAttribute("point", 102920122);

point It's digital , Use ${point} The value of this number will be displayed , Use commas to separate every three digits .

If you don't want to display numbers separated by every three digits , have access to c Function converts a numeric type to a string and outputs

${point?c}

6.4： take json String to object

An example ：

Which USES assign label ,assign The function of is to define a variable .

<#assign text="{'bank':' Industrial and Commercial Bank of China ','account':'10101920201920212'}" />
<#assign data=text?eval />
 Opening bank ：${data.bank}   account number ：${data.account}

7.🧩 Static testing

Previous tests have been SpringMVC take Freemarker As a view parser （ViewReporter） To integrate into the project , In the work , Sometimes you need to use Freemarker Native Api To generate static content , Now let's learn about native Api Generate text file ( Select generate here html file ).

7.1： modify application.yml file

Add the configuration information of the following template storage location , The full configuration is as follows ：

server:
  port: 8881 # Service port 
spring:
  application:
    name: freemarker-demo # Specify the service name 
  freemarker:
    cache: false  # Turn off template caching , Convenient test 
    settings:
      template_update_delay: 0 # Check the template update delay time , Set to 0 Means to check immediately , If the time is longer than 0 There will be caches that are not convenient for template testing 
    suffix: .ftl               # Appoint Freemarker The suffix of the template file 
    template-loader-path: classpath:/templates   # Template storage location

7.2： stay test Create a test class

package com.my.freemarker.test;

import com.my.freemarker.FreemarkerApplication;
import com.my.freemarker.entity.Student;
import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import org.junit.jupiter.api.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.io.FileWriter;
import java.io.IOException;
import java.util.*;

@SpringBootTest(classes = FreemarkerApplication.class)
@RunWith(SpringRunner.class)
public class FreemarkerTest {
    @Autowired
    private Configuration configuration;

    @Test
    public void test() throws IOException, TemplateException {
        //freemarker Template object , Access to the template 
        Template template = configuration.getTemplate("02-list.ftl");
        Map params = getData();

        template.process(params,new FileWriter("d:/headlinesPro/list.html"));
    }

    private Map getData() {
        Map<String,Object> map = new HashMap<>();

        // Data model construction 
        Student stu1 = new Student();
        stu1.setName(" cockroach ");
        stu1.setAge(19);
        stu1.setMoney(100F);
        stu1.setBirthday(new Date());

        Student stu2 = new Student();
        stu2.setName(" Xiaohong ");
        stu2.setAge(20);
        stu2.setMoney(1000F);
        stu2.setBirthday(new Date());

        // Put two objects into List
        List<Student> list = new ArrayList<>();
        list.add(stu1);
        list.add(stu2);

        // towards map In the store list data 
        map.put("stus",list);

        // establish mao data 
        HashMap<String,Student> stuMap = new HashMap<>();
        stuMap.put("stu1",stu1);
        stuMap.put("stu2",stu2);
        // towards Map In the store Map data 
        map.put("stuMap",stuMap);

        return map;
    }
}