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Freemaker template engine

2022-07-25 08:30:00 【Two kings and one today】

freemarker Introduce

FreeMarker It's 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 , No image 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 What other template engines are there ？

Jsp、Freemarker、Thymeleaf 、Velocity etc. .

Jsp by Servlet special , Cannot be used alone .
Thymeleaf For new technology , More powerful , But the efficiency of implementation is relatively low .
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 .

Page rendering process

Use dependency ：

<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>

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

The 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

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>

<ul>
    <#-- Sentenced to empty 、 Conditions 、 A collection of traverse -->
</ul>

<#-- Arithmetic operations 、 Compare 、 Logical operations -->

<#-- Built in functions -->

</body>
</html>

establish controller

establish Controller class , towards Map Add name, Finally, return to the template file .

package com.heima.demo.freemarker.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.client.RestTemplate;

import java.util.Map;

@Controller
public class HelloController {

    @GetMapping("/basic")
    public String test(Model model) {
        //1. Parameters in plain text 
        model.addAttribute("name", "freemarker");
        //2. Parameters related to entity classes 
        Map<String, Object> student = new HashMap<>();
        student.put("name"," Xiao Ming ");
        student.put("age", 18);
        model.addAttribute("stu", student);

        return "01-basic";
    }
}

Create startup class

package com.heima.demo.freemarker;

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

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