254 lines
9.7 KiB
Markdown
254 lines
9.7 KiB
Markdown
# Spring-Boot 基础
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<nav>
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<a href="#一项目说明">一、项目说明</a><br/>
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<a href="#11-项目结构">1.1 项目结构</a><br/>
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<a href="#12-基本依赖">1.2 基本依赖</a><br/>
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<a href="#二主启动类">二、主启动类</a><br/>
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<a href="#三开箱即用">三、开箱即用</a><br/>
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<a href="#四模板引擎">四、模板引擎</a><br/>
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<a href="#41-freemarker">4.1 freemarker</a><br/>
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<a href="#42-thymeleaf">4.2 thymeleaf</a><br/>
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<a href="#43-文档说明">4.3 文档说明</a><br/>
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</nav>
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## 一、项目说明
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### 1.1 项目结构
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1. 本项目搭建一个简单的 hello spring 的 Web 工程，简单说明 Spring-Boot 的开箱即用的特性；
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2. 模板引擎采用 freemaker 和 thymeleaf 作为示例，分别对应模板文件 makershow.ftl 和 leafShow.html；
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3. Spring Boot 2.x 默认不支持 Jsp ，需要额外的配置，关于使用 jsp 的整合可以参考 [spring-boot-jsp](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-boot/spring-boot-jsp) 项目。
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-boot-base.png"/> </div>
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### 1.2 基本依赖
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导入相关的 starter (启动器)：
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-parent</artifactId>
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<version>2.1.1.RELEASE</version>
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<relativePath/> <!-- lookup parent from repository -->
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</parent>
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<groupId>com.heibaiying</groupId>
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<artifactId>spring-boot-base</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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<name>spring-boot-base</name>
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<description>Demo project for Spring Boot</description>
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<properties>
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<java.version>1.8</java.version>
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</properties>
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<dependencies>
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<!--模板引擎-->
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-freemarker</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-thymeleaf</artifactId>
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</dependency>
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<!--web 启动器-->
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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</dependency>
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<!--lombok 插件-->
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<optional>true</optional>
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</dependency>
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<!--测试相关依赖-->
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-test</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<!--Spring Boot 的 Maven 插件（Spring Boot Maven plugin）能够以 Maven 的方式为应用提供 Spring Boot 的支持-->
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<build>
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<plugins>
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<plugin>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-maven-plugin</artifactId>
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</plugin>
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</plugins>
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</build>
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</project>
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```
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+ Spring Boot 项目默认继承自 spring-boot-starter-parent，而 spring-boot-starter-parent 则继承自 spring-boot-dependencies，spring-boot-dependencies 中定义了关于 spring boot 依赖的各种 jar 包的版本，它是 Spring Boot 的版本管理中心。
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-boot-dependencies.png"/> </div>
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+ 关于Spring Boot 2.x 官方支持的所有 starter 可以参见官方文档：[Table 13.1. Spring Boot application starters](https://docs.spring.io/spring-boot/docs/2.1.1.RELEASE/reference/htmlsingle/#using-boot-starter)
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## 二、主启动类
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如果采用 IDEA 或者 Spring Tool Suite (STS) 等开发工具创建的 Spring Boot 工程，会默认创建启动类，如果没有创建，需要手动创建启动类：
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```java
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package com.heibaiying.springbootbase;
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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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@SpringBootApplication
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public class SpringBootBaseApplication {
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// 启动类默认开启包扫描，扫描与主程序所在包及其子包，对于本工程而言 默认扫描 com.heibaiying.springbootbase
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public static void main(String[] args) {
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SpringApplication.run(SpringBootBaseApplication.class, args);
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}
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}
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```
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@SpringBootApplication 是一个复合注解，里面包含了 @ComponentScan 注解，即默认开启包扫描，扫描主程序所在包及其子包，对于本工程而言，默认扫描 com.heibaiying.springbootbase：
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```java
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@Target(ElementType.TYPE)
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@Inherited
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@SpringBootConfiguration
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@EnableAutoConfiguration
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@ComponentScan(excludeFilters = {
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@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
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@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
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public @interface SpringBootApplication {
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...
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}
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```
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## 三、开箱即用
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采用 Spring Boot 构建的 Web 项目具备开箱即用的特性，不需要做任何额外的配置就可以正常使用。这里我们在 springbootBaseApplication 的同级目录创建 controller 文件夹，并在其中创建 RestfulController 控制器，之后启动项目访问 `localhost:8080/restful/programmers` ，即可看到返回相关的信息。
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```java
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@RestController
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@RequestMapping("restful")
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public class RestfulController {
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@GetMapping("programmers")
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private List<Programmer> getProgrammers() {
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List<Programmer> programmers = new ArrayList<>();
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programmers.add(new Programmer("xiaoming", 12, 100000.00f, LocalDate.of(2019, Month.AUGUST, 2)));
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programmers.add(new Programmer("xiaohong", 23, 900000.00f, LocalDate.of(2013, Month.FEBRUARY, 2)));
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return programmers;
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}
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}
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```
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Spring Boot 之所以能够开箱即用，是因为我们在项目中导入 spring-boot-starter-web 启动器，而 @SpringBootApplication 复合注解中默认开启了 @EnableAutoConfiguration ，即允许开启自动化配置。 Spring Boot 检查到存在 starter-web 依赖后就会开启 Web 相关的自动化配置。
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## 四、模板引擎
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这里我们在一个项目中同时导入了 freemaker 和 thymeleaf 的 starter（虽然并不推荐，但是在同一个项目中是可以混用这两种模板引擎的）:
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### 4.1 freemarker
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```java
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/**
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* @description : 跳转渲染模板引擎 默认模板的存放位置为 classpath:templates
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*/
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@Controller
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@RequestMapping("freemarker")
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public class FreeMarkerController {
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@RequestMapping("show")
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private String programmerShow(ModelMap modelMap){
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List<Programmer> programmerList=new ArrayList<>();
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programmerList.add(new Programmer("xiaoming",12,100000.00f,LocalDate.of(2019,Month.AUGUST,2)));
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programmerList.add(new Programmer("xiaohong",23,900000.00f,LocalDate.of(2013,Month.FEBRUARY,2)));
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modelMap.addAttribute("programmers",programmerList);
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return "markerShow";
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}
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}
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```
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```html
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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>freemarker 模板引擎</title>
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</head>
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<body>
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<ul>
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<#list programmers as programmer>
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<li>姓名: ${programmer.name} 年龄: ${programmer.age}</li>
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</#list>
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</ul>
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</body>
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</html>
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```
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### 4.2 thymeleaf
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```java
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/**
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* @description : 跳转渲染模板引擎 默认模板的存放位置为 classpath:templates
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*/
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@Controller
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@RequestMapping("thymeleaf")
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public class ThymeleafController {
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@RequestMapping("show")
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private String programmerShow(ModelMap modelMap) {
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List<Programmer> programmerList = new ArrayList<>();
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programmerList.add(new Programmer("xiaoming", 12, 100000.00f, LocalDate.of(2019, Month.AUGUST, 2)));
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programmerList.add(new Programmer("xiaohong", 23, 900000.00f, LocalDate.of(2013, Month.FEBRUARY, 2)));
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modelMap.addAttribute("programmers", programmerList);
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return "leafShow";
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}
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}
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```
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```html
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<!doctype html>
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<html lang="en" xmlns:th="http://www.thymeleaf.org">
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<head>
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<meta charset="UTF-8">
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<title>thymeleaf 模板引擎</title>
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</head>
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<body>
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<ul th:each="programmer:${programmers}">
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<li>
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姓名:<span th:text="${programmer.name}"></span>
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薪水:<span th:text="${programmer.salary}"></span>
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</li>
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</ul>
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</body>
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</html>
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```
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### 4.3 文档说明
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关于这两种模板引擎的语法可以参考其官方文档：
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- **freemarker**：提供了完善的中文文档，地址为： http://freemarker.foofun.cn/ 。
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- **thymeleaf**：官方英文文档地址：[thymeleaf 3.0.11RELEASE](https://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.pdf) 。我在本仓库中上传了一份 [thymeleaf 中文文档（gangzi828(刘明刚 译）](https://github.com/heibaiying/spring-samples-for-all/tree/master/referenced%20documents)，翻译的版本为 3.0.5RELEASE。
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