Javalin 旨在为 Kotlin 和 Java 提供一个易用的轻量级 REST API 库。这个 REST API 易于使用,API 也非常的流畅。
Javalin 主要有以下的特点:
-  
易用:不用提前学习任何概念就可以开始使用
 -  
一致的 API:所有的处理程序和映射器在 Context (ctx) 中都是无效的。
 -  
Kotlin 和 Java 拥有几乎完全相同的 API
 -  
是框架也是库:无需扩展任何功能
 -  
拥有完全可定制的嵌入式服务器 (Jetty)
 -  
JSON 对象映射
 -  
通过 AccessManager 接口简单的按端点验证
 -  
简单的静态文件处理
 -  
生命周期事件
 -  
CookieStore,一种简单的用来序列化的方法和存储在 cookie 中的对象。
 -  
模板渲染
 -  
Markdown 渲染
 
下面是用 Kotlin 实现的 “Hello World” API 的例子。
import io.javalin.Javalin;
public class HelloWorld {
    public static void main(String[] args) {
        var app = Javalin.create(/*config*/)
            .get("/", ctx -> ctx.result("Hello World"))
            .start(7070);
    }
}
 
Request Handler 每个请求处理,或者匹配某些路径处理:
app.before(ctx -> {
    // runs before all requests
});
app.before("/path/*", ctx -> {
    // runs before request to /path/*
});
 
请求处理:
app.get("/output", ctx -> {
    // some code
    ctx.json(object);
});
app.post("/input", ctx -> {
    // some code
    ctx.status(201);
});
 
Javalin官网文档地址
 下面基于Javalin和springboot、Mybatis-Flex(Mybatis-Flex官网文档)实现一个简单的项目:
 项目结构:
 
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.kexuexiong</groupId>
    <artifactId>shushan_server</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <java.version>17</java.version>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>
        <dependency>
            <groupId>com.mybatis-flex</groupId>
            <artifactId>mybatis-flex-spring-boot-starter</artifactId>
            <version>1.5.3</version>
        </dependency>
        <dependency>
            <groupId>com.mybatis-flex</groupId>
            <artifactId>mybatis-flex-processor</artifactId>
            <version>1.5.3</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>io.javalin</groupId>
            <artifactId>javalin</artifactId>
            <version>5.6.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter-test</artifactId>
            <version>3.0.2</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.zaxxer</groupId>
            <artifactId>HikariCP</artifactId>
            <version>4.0.3</version>
        </dependency>
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.8.16</version>
        </dependency>
        <dependency>
            <groupId>com.mybatis-flex</groupId>
            <artifactId>mybatis-flex-codegen</artifactId>
            <version>1.5.3</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>2.0.7</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>
 
application.yml
spring:
  datasource:
    url: jdbc:mysql://数据库ip:3306/shushan
    username: root
    password: 密码
mybatis-flex:
  mapper-locations:
    - classpath*:/mappers/*.xml
 
Application.java
package com.kexuexiong;
import io.javalin.Javalin;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import java.util.logging.Logger;
@SpringBootApplication
@MapperScan("com.kexuexiong.mapper")
public class ShuShanApplication {
    private  static Logger LOGGER = Logger.getLogger(ShuShanApplication.class.getName());
    public static void main(String[] args) {
       SpringApplication.run(ShuShanApplication.class, args);
    }
    @Bean
    public Javalin init(){
        Javalin app = Javalin.create(/*config*/)
                .get("/", ctx -> ctx.result("Hello World"))
                .start(7070);
        return app;
    }
}
 
逆向工程工具:
package com.kexuexiong.common.utils;
import com.mybatisflex.codegen.Generator;
import com.mybatisflex.codegen.config.ColumnConfig;
import com.mybatisflex.codegen.config.GlobalConfig;
import com.zaxxer.hikari.HikariDataSource;
public class Codegen {
    public static void main(String[] args) {
        //配置数据源
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl("jdbc:mysql://数据库ip:3306/shushan?characterEncoding=utf-8");
        dataSource.setUsername("root");
        dataSource.setPassword("密码");
        //创建配置内容,两种风格都可以。
        GlobalConfig globalConfig = createGlobalConfigUseStyle1();
        //GlobalConfig globalConfig = createGlobalConfigUseStyle2();
        //通过 datasource 和 globalConfig 创建代码生成器
        Generator generator = new Generator(dataSource, globalConfig);
        //生成代码
        generator.generate();
    }
    public static GlobalConfig createGlobalConfigUseStyle1() {
        //创建配置内容
        GlobalConfig globalConfig = new GlobalConfig();
        //设置根包
        globalConfig.setBasePackage("com.kexuexiong");
        //设置表前缀和只生成哪些表
        globalConfig.setGenerateSchema("shushan");
        globalConfig.setTablePrefix("");
        globalConfig.setGenerateTable("demo");
        //设置生成 entity 并启用 Lombok
        globalConfig.setEntityGenerateEnable(true);
        globalConfig.setEntityWithLombok(true);
        //设置生成 mapper
        globalConfig.setMapperGenerateEnable(true);
        globalConfig.setAuthor("kexuexiong");
        globalConfig.setControllerGenerateEnable(true);
        globalConfig.setServiceGenerateEnable(true);
        globalConfig.setMapperXmlGenerateEnable(true);
        globalConfig.setMapperXmlPath("src/main/resources/mappers");
        globalConfig.setServiceImplGenerateEnable(true);
        //可以单独配置某个列
        ColumnConfig columnConfig = new ColumnConfig();
        columnConfig.setLarge(true);
        columnConfig.setVersion(true);
        return globalConfig;
    }
    public static GlobalConfig createGlobalConfigUseStyle2() {
        //创建配置内容
        GlobalConfig globalConfig = new GlobalConfig();
        //设置根包
        globalConfig.getPackageConfig()
                .setBasePackage("com.kexuexiong");
        //设置表前缀和只生成哪些表,setGenerateTable 未配置时,生成所有表
        globalConfig.getStrategyConfig()
                .setGenerateSchema("shushan")
                .setTablePrefix("")
                .setGenerateTable("demo");
        //设置生成 entity 并启用 Lombok
        globalConfig.enableEntity()
                .setWithLombok(true);
        //设置生成 mapper
        globalConfig.enableMapper();
        //可以单独配置某个列
        ColumnConfig columnConfig = new ColumnConfig();
        columnConfig.setColumnName("tenant_id");
        columnConfig.setLarge(true);
        columnConfig.setVersion(true);
        globalConfig.getStrategyConfig()
                .setColumnConfig("account", columnConfig);
        return globalConfig;
    }
}
 
运行该工具类可以生成代码:
 
 编写controller类:
package com.kexuexiong.controller;
import cn.hutool.json.JSONUtil;
import com.kexuexiong.entity.Demo;
import com.kexuexiong.service.DemoService;
import io.javalin.Javalin;
import jakarta.annotation.PostConstruct;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.List;
@Component
@Slf4j
public class DemoController {
    @Autowired
    private Javalin app;
    @Autowired
    private DemoService demoService;
    @PostConstruct
    public void test(){
        app.get("/hello/{name}", ctx -> {
            List<Demo> list = demoService.list();
            log.info(JSONUtil.toJsonStr(list.toString()));
            ctx.result("Hello: ");
        });
    }
}
 
启动程序:
 
 Javalin应用在一些小项目还是可以的,轻量级。

















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