《Kotlin 程序设计》第八章 Kotlin 集成Spring Boot开发

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第八章 Kotlin 集成Spring Boot开发

Java整个生态系统经过近20年的发展，已经非常成熟完整了。相对于年轻的Kotlin而言，我们不可能一下子抛弃整个Java生态系统。至少在目前，运行在全世界的互联网服务器上的大多数服务依然是整个Java生态的天下。

然而，在Java生态中最为出色的莫过于Spring框架体系了。尤其是近两年来，Spring Boot以及微服务的出现，使得Spring框架更加出色。

在Spring 5 中，已经增加了使用Kotlin的实现。

使用Kotlin 与 Spring Boot 开发真的是如丝般润滑。本章我们介绍使用Kotlin + Spring Boot创建一个RESTful服务，并开发一个简单的Web系统。

Step1. html页面加入头文件相应的schema

<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">

Step2.主页面模板

<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><th:block th:include="common/header :: head"></th:block><body><th:block th:include="common/header :: header"></th:block><div th:if="${not #lists.isEmpty(customers)}">    <h2>Customer List</h2>    <table id="customersTable" class="table table-striped">        <thead>        <tr>            <th>Id</th>            <th>FirstName</th>            <th>LastName</th>            <th>Created Time</th>        </tr>        </thead>        <tbody>        <tr th:each="customer : ${customers}">            <td th:text="${customer.id}"><a href="/product/${product.id}">Id</a></td>            <td th:text="${customer.firstName}">FirstName</td>            <td th:text="${customer.lastName}">LastName</td>            <td th:text="${customer.gmtCreated}">gmtCreated</td>            <!--<td><a th:href="${ '/product/' + product.id}">View</a></td>-->            <!--<td><a th:href="${'/product/edit/' + product.id}">Edit</a></td>-->        </tr>        </tbody>    </table></div><th:block th:include="common/footer :: footer"></th:block></body></html>

Step3.include common模板说明

common/header.html

<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><head lang="en" th:fragment="head">    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>    <link href="http://cdn.jsdelivr.net/webjars/bootstrap/3.3.4/css/bootstrap.min.css"          th:href="@{/webjars/bootstrap/3.3.4/css/bootstrap.min.css}"          rel="stylesheet" media="screen"/>    <link href="../../static/css/jquery.dataTables.min.css"          th:href="@{css/jquery.dataTables.min.css}" rel="stylesheet" media="screen"/>    <link href="../../static/css/mini_springboot.css"          th:href="@{css/mini_springboot.css}" rel="stylesheet" media="screen"/>    <title>Mini SpringBoot Tutorial</title></head><body><div th:fragment="header">    <nav class="navbar navbar-default">        <div class="container-fluid">            <div class="navbar-header">                <a class="navbar-brand" href="#" th:href="@{/}">Home</a>                <ul class="nav navbar-nav">                    <li><a href="#" th:href="@{/customers.do}">Customers</a></li>                    <li><a href="#" th:href="@{/customer/new}">Create Customer</a></li>                </ul>            </div>        </div>    </nav>    <div class="jumbotron">        <div class="row text-center">            <div class="">                <h1 class="center">Springboot极简教程</h1>                <h2>Mini SpringBoot Tutorial</h2>                <h3>Spring Boot Kotlin Thymeleaf Web App</h3>            </div>        </div>        <div class="row text-center">            <iframe class="iframe" src="https://jason-chen-2017.github.io/Jason-Chen-2017/"></iframe>            <!--![](../../static/images/home.png)-->        </div>    </div></div></body></html>

common/footer.html

<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><head lang="en">    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/></head><body><div th:fragment="footer">    <div class="footer">Springboot极简教程, Jason Chen, 2017</div>    <script src="http://cdn.jsdelivr.net/webjars/jquery/2.1.4/jquery.min.js"            th:src="@{/webjars/jquery/2.1.4/jquery.min.js}"></script>    <script src="http://cdn.jsdelivr.net/webjars/bootstrap/3.3.4/js/bootstrap.min.js"            th:src="@{/webjars/bootstrap/3.3.4/js/bootstrap.min.js}"></script>    <script src="../../static/js/jquery.dataTables.min.js"            th:src="@{js/jquery.dataTables.min.js}"></script>    <script src="../../static/js/mini_springboot.js" th:src="@{js/mini_springboot.js}"></script></div></body></html>

重点看一下thymeleaf的语法设计风格。

写一个th:fragment="{id}"

<div th:fragment="footer">    。。。</div>

可以直接在其他页面 th:include

<th:block th:include="common/footer :: footer"></th:block>

Step4. 配置build.gradle，添加spring-boot-starter-thymeleaf

Spring Boot默认就是使用thymeleaf模板引擎的，所以只需要在build.gradle（pom.xml）加入依赖即可。

version = "0.0.1-SNAPSHOT"buildscript {    ext {        springBootVersion = "1.5.2.RELEASE"        kotlinVersion = "1.1.0"    }    repositories {        mavenCentral()    }    dependencies {        classpath("org.springframework.boot:spring-boot-gradle-plugin:$springBootVersion")        classpath("org.jetbrains.kotlin:kotlin-noarg:$kotlinVersion")        classpath("org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion")        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")    }}apply {    plugin("kotlin")    plugin("kotlin-spring")    plugin("kotlin-jpa")    plugin("org.springframework.boot")    plugin 'java'    plugin 'eclipse'    plugin 'idea'//    plugin: 'spring-boot'}repositories {    mavenCentral()}jar {    baseName = 'mini_springboot'    version = '0.0.1'}sourceCompatibility = 1.8targetCompatibility = 1.8dependencies {    compile("org.springframework.boot:spring-boot-starter-data-jpa")//    compile("com.h2database:h2")    compile("org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion")    compile("org.jetbrains.kotlin:kotlin-reflect:$kotlinVersion")    compile("com.fasterxml.jackson.module:jackson-module-kotlin:2.8.4")    testCompile("org.springframework.boot:spring-boot-starter-test")    compile("org.springframework.boot:spring-boot-starter-web") {        exclude module: "spring-boot-starter-tomcat"    }    compile("org.springframework.boot:spring-boot-starter-jetty")    compile("org.springframework.boot:spring-boot-starter-actuator")    compile('mysql:mysql-connector-java:5.1.13')    testCompile("junit:junit")//thymeleaf    compile("org.springframework.boot:spring-boot-starter-thymeleaf")//WebJars    compile("org.webjars:bootstrap:3.3.4")    compile("org.webjars:jquery:2.1.4")    // https://mvnrepository.com/artifact/org.webjars/datatables    compile group: 'org.webjars', name: 'datatables', version: '1.10.13'}

Step5. 新建标准springboot resources目录

Springboot web app有很多约定，根据这些约定，可以省去一大批繁冗的配置。请看标准的工程目录结构

.├── META-INF│   └── MANIFEST.MF├── README.md├── README_.md├── build│   └── kotlin-build│       └── caches│           └── version.txt├── build.gradle├── gradle│   └── wrapper│       ├── gradle-wrapper.jar│       └── gradle-wrapper.properties├── gradlew├── gradlew.bat├── run.bat├── run.sh├── settings.gradle└── src    ├── main    │   ├── java    │   ├── kotlin    │   │   └── jason    │   │       └── chen    │   │           └── mini_springboot    │   │               ├── console    │   │               │   └── HelloWorld.kt    │   │               └── restful    │   │                   ├── Application.kt    │   │                   ├── biz    │   │                   │   └── CustomerService.kt    │   │                   ├── controller    │   │                   │   └── CustomerController.kt    │   │                   ├── entity    │   │                   │   └── Customer.kt    │   │                   └── utils    │   │                       └── DateUtils.kt    │   └── resources    │       ├── application.properties    │       ├── application.yml    │       ├── static    │       │   ├── css    │       │   │   ├── jquery.dataTables.min.css    │       │   │   └── mini_springboot.css    │       │   ├── images    │       │   │   ├── home.png    │       │   │   ├── sort_asc.png    │       │   │   ├── sort_both.png    │       │   │   └── sort_desc.png    │       │   └── js    │       │       ├── jquery.dataTables.min.js    │       │       └── mini_springboot.js    │       └── templates    │           ├── common    │           │   ├── footer.html    │           │   └── header.html    │           ├── customers.html    │           ├── index.html    │           ├── productform.html    │           ├── products.html    │           └── productshow.html    └── test        ├── java        ├── kotlin        └── resources30 directories, 35 files

Step5. 写Controller

package jason.chen.mini_springboot.restful.controllerimport jason.chen.mini_springboot.restful.biz.CustomerServiceimport org.springframework.stereotype.Controllerimport org.springframework.ui.Modelimport org.springframework.web.bind.annotation.GetMappingimport org.springframework.web.bind.annotation.PathVariableimport org.springframework.web.bind.annotation.ResponseBody@Controllerclass CustomerController(val customerService: CustomerService) {    @GetMapping(value = "/")    fun index(): String {        return "index"    }    @GetMapping("/customers.do")    fun listAll(model: Model): String {        val allCustomers = customerService.findAll()        model.addAttribute("customers", allCustomers)        return "customers"    }    @GetMapping("/listCustomers")    @ResponseBody    fun listCustomers(model: Model) = customerService.findAll()    @GetMapping("/{lastName}")    @ResponseBody    fun findByLastName(@PathVariable lastName: String)            = customerService.findByLastName(lastName)}