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Java与kotlin混合编程时的maven配置

发表于 更新于 分类于 Valine：
本文字数： 13k 阅读时长 ≈ 12 分钟

kotlin官方文档： https://kotlinlang.org/docs/maven.html

A. 项目结构:

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Demo
├── demo-client
│   ├── src
│   ├── pom.xml
├── demo-application
│   ├── pom.xml
│   ├── src
│   │   ├── main
│   │   │   ├── java
│   │   │   └── kotlin
├── demo-domain
│   ├── pom.xml
│   ├── src
│   │   ├── main
│   │   │   ├── java
│   │   │   └── kotlin
├── demo-external
│   ├── src
│   ├── pom.xml
├── demo-infrastructure
│   ├── pom.xml
│   ├── src
├── demo-start
│   ├── src
│   ├── pom.xml
├── pom.xml

这是一个包含多个子模块的maven项目。我这里目前只在demo-application和demo-domain中同时使用了kotlin和java，不过已经足够证明混合编程的可能性。

B. 目前项目使用的java版本为1.8，kotlin版本为1.6.10，其中项目最外层pom.xml的部分配置如下:

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<name>Demo</name>
<groupId>com.leuncle.demo</groupId>
<artifactId>Demo-parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>pom</packaging>

<properties>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.source>1.8</maven.compiler.source>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <org.mapstruct.version>1.4.2.Final</org.mapstruct.version>
    <spring-boot.version>2.1.3.RELEASE</spring-boot.version>
    <kotlin.version>1.6.10</kotlin.version>
    <kotlin.code.style>official</kotlin.code.style>
    <kotlin.compiler.apiVersion>1.6</kotlin.compiler.apiVersion>
</properties>

<modules>
    <module>demo-start</module>
    <module>demo-client</module>
    <module>demo-external</module>
    <module>demo-application</module>
    <module>demo-domain</module>
    <module>demo-infrastructure</module>
</modules>

<dependencyManagement>
    <dependencies>
       <!-- Log4j2 -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-bom</artifactId>
            <version>2.16.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <!-- Project modules -->
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-client</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-external</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-application</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-domain</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-infrastructure</artifactId>
            <version>${project.version}</version>
        </dependency>
        <!--SpringBoot-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>${spring-boot.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <!-- lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.16</version>
        </dependency>
        <!-- mapstruct -->
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
            <version>${org.mapstruct.version}</version>
        </dependency>
        <!-- kotlin -->
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk7</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-common</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
            <version>2.9.8</version>
        </dependency>
    </dependencies>
</dependencyManagement>
<build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>lombok</plugin>
                        <plugin>spring</plugin>
                        <plugin>all-open</plugin>
                    </compilerPlugins>
                    <jvmTarget>1.8</jvmTarget>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-lombok</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <id>compile</id>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <sourceDir>src/main/kotlin</sourceDir>
                                <sourceDir>src/main/java</sourceDir>
                            </sourceDirs>
                        </configuration>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <sourceDir>src/test/kotlin</sourceDir>
                                <sourceDir>src/test/java</sourceDir>
                            </sourceDirs>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>1.18.16</version>
                        </path>
                        <path>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok-mapstruct-binding</artifactId>
                            <version>0.2.0</version>
                        </path>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>1.4.2.Final</version>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
                <executions>
                    <!-- Replacing default-compile as it is treated specially by maven -->
                    <execution>
                        <id>default-compile</id>
                        <phase>none</phase>
                    </execution>
                    <!-- Replacing default-testCompile as it is treated specially by maven -->
                    <execution>
                        <id>default-testCompile</id>
                        <phase>none</phase>
                    </execution>
                    <execution>
                        <id>java-compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>java-test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-source-plugin</artifactId>
                <version>${plugin.source.version}</version>
                <executions>
                    <execution>
                        <id>attach-sources</id>
                        <phase>verify</phase>
                        <goals>
                            <goal>jar-no-fork</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </pluginManagement>
</build>

上面的内容中值得注意的主要是build部分，pluginManagement主要用于定义各种插件的配置信息，并不会实际引入，需要在各个子模块中按需引入，子模块中只需要声明groupId和artifactId即可。

  1. kotlin-maven-lombok：处理kotlin代码转换与lombok注解处理的先后关系，没有它，如果在同一个模块中，kotlin代码里面用到了java代码中的类，而该类使用了lombok注解，那就会有问题。

  2. allopen：kotlin中所有的类默认都是不可继承，spring框架的代理就不好使了。所以kotlin代码里会满满的open。这个插件可以省掉这些open，为指定注解注解的类在编译时添加open。以上面的配置为例，可以在compilerPlugins和jvmTarget之间加上下面的配置，即可让被Entity注解所注解的类默认open。

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    <pluginOptions>
      <option>all-open:annotation=javax.persistence.Entity</option>
    </pluginOptions>

  3. spring：这个其实就是已经指定一些spring常用注解来添加open。本质上也是依赖allopen插件的。该插件指定了以下注解： @Component、 @Async、 @Transactional、 @Cacheable 以及 @SpringBootTest。由于元注解的支持，标注有 @Configuration、 @Controller、 @RestController、 @Service 或者 @Repository 的类会自动打开，因为这些注解标注有元注解@Component。

  4. no-arg：该插件为具有特定注解的类生成一个额外的零参数构造函数。这个生成的构造函数是合成的，因此不能从 java或kotlin中直接调用，但可以使用反射调用。这允许Java Persistence API（JPA）实例化一个类，就算它从 kotlin 或 java的角度看没有无参构造函数。

  5. maven打包成功，但是本地直接点击IDEA的Debug/Run还是报错，类似于:

​ Lombok requires enabled annotation processing: Do you want to enable annotation processors?

​ 依次点击setting –> Build，Execution，Deployment –>Annotation Processors打开编辑页面，勾上Enable annotation processing前面的勾，保存后需要重启IDEA

C. 子模块pom.xml

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<?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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.leuncle.demo</groupId>
        <artifactId>Demo-parent</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>demo-domain</artifactId>
    <packaging>jar</packaging>
    <name>demo-domain</name>

    <dependencies>
        <!-- service models -->
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-infrastructure</artifactId>
        </dependency>
        <dependency>
            <groupId>com.leuncle.demo</groupId>
            <artifactId>demo-external</artifactId>
        </dependency>

        <!-- mapstruct -->
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
        </dependency>

        <!-- kotlin -->
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk7</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-common</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

每个子模块需要单独引入kotlin的依赖。

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