java - 为什么不解决其他模块的 mysql 依赖关系

标签 java mysql maven

我有多模块java项目。数据库逻辑位于一个模块中(常见)，restapi Web 应用程序位于另一模块中(restapi)。我在restapi模块中的公共(public)模块中调用方法时遇到问题。不解决公共(public)模块 pom 中的 mysql 依赖关系。

这是我的pom.xml
对于根

<?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>

    <groupId>qwerty.project</groupId>
    <artifactId>project</artifactId>
    <version>0.1</version>
    <modules>
        <module>common</module>
        <module>restapi</module>
    </modules>
    <packaging>pom</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

对于通用模块

<?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">
    <parent>
        <artifactId>project</artifactId>
        <groupId>qwerty.project</groupId>
        <version>0.1</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <name>common</name>
    <packaging>jar</packaging>
    <artifactId>qwerty.common</artifactId>

    <dependencies>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.12</version>
        </dependency>
    </dependencies>
</project>

这是用于restapi模块的

<?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">
    <parent>
        <artifactId>project</artifactId>
        <groupId>qwerty.project</groupId>
        <version>0.1</version>
        <relativePath>../pom.xml</relativePath>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>rest-api</artifactId>
    <dependencies>
        <dependency>
            <groupId>qwerty.project</groupId>
            <artifactId>qwerty.common</artifactId>
            <version>0.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.jayway.jsonpath</groupId>
            <artifactId>json-path</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>1.5.6.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

在我的restapi Controller 中，我要从公共(public)模块注入(inject)Dao。 

@RestController
public class VideoController {

    @Autowired
    VideoDAO videoDAO;

    @RequestMapping("/video")
    public String getVideo() throws SQLException {
        List<String> links = videoDAO.doSome();
        return links.get(0); 
    }
}

我正在进行 mvn 全新安装 如果我启动 Spring Boot 应用程序(来自模块 RestAPI)，我会在日志中看到公共(public)模块中的 c3p0 已成功初始化。但 mysql 不是，-NoClassFoundException。为什么会出现这种情况？ 

2018-10-12 11:34:34.060  WARN 10160 --- [HelperThread-#2] c.m.v2.c3p0.DriverManagerDataSource      : Could not load driverClass com.mysql.cj.jdbc.Driver
java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_144]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_144]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) ~[na:1.8.0_144]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_144]

jdbc类在资源中的设置文件的公共(public)模块中声明

c3p0.driverClass=com.mysql.cj.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/Some
c3p0.user=***
c3p0.password=***
c3p0.initialPoolSize=5
c3p0.minPoolSize=5
...

我注意到，如果 mysql 依赖项转移到根 pom 文件，项目就会开始正常工作。 但我认为这不是一个好主意，因为逻辑上 mysql 应该位于公共(public)模块中。 我将不胜感激您的建议

更新 restapi 模块的依赖树 

qwerty.project:rest-api:jar:0.1
[INFO] +- qwerty.project:qwerty.common:jar:0.1:compile
[INFO] |  +- com.mchange:c3p0:jar:0.9.5.2:compile
[INFO] |  |  \- com.mchange:mchange-commons-java:jar:0.2.11:compile
[INFO] |  \- mysql:mysql-connector-java:jar:5.1.43:compile
[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:1.5.6.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter:jar:1.5.6.RELEASE:compile
[INFO] |  |  +- org.springframework.boot:spring-boot:jar:1.5.6.RELEASE:compile
[INFO] |  |  +- org.springframework.boot:spring-boot-autoconfigure:jar:1.5.6.RELEASE:compile
[INFO] |  |  +- org.springframework.boot:spring-boot-starter-logging:jar:1.5.6.RELEASE:compile
[INFO] |  |  |  +- ch.qos.logback:logback-classic:jar:1.1.11:compile
[INFO] |  |  |  |  \- ch.qos.logback:logback-core:jar:1.1.11:compile
[INFO] |  |  |  +- org.slf4j:jcl-over-slf4j:jar:1.7.25:compile
[INFO] |  |  |  +- org.slf4j:jul-to-slf4j:jar:1.7.25:compile
[INFO] |  |  |  \- org.slf4j:log4j-over-slf4j:jar:1.7.25:compile
[INFO] |  |  \- org.yaml:snakeyaml:jar:1.17:runtime
[INFO] |  +- org.springframework.boot:spring-boot-starter-tomcat:jar:1.5.6.RELEASE:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-core:jar:8.5.16:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-el:jar:8.5.16:compile
[INFO] |  |  \- org.apache.tomcat.embed:tomcat-embed-websocket:jar:8.5.16:compile
[INFO] |  +- org.hibernate:hibernate-validator:jar:5.3.5.Final:compile
[INFO] |  |  +- javax.validation:validation-api:jar:1.1.0.Final:compile
[INFO] |  |  +- org.jboss.logging:jboss-logging:jar:3.3.1.Final:compile
[INFO] |  |  \- com.fasterxml:classmate:jar:1.3.3:compile
[INFO] |  +- com.fasterxml.jackson.core:jackson-databind:jar:2.8.9:compile
[INFO] |  |  +- com.fasterxml.jackson.core:jackson-annotations:jar:2.8.0:compile
[INFO] |  |  \- com.fasterxml.jackson.core:jackson-core:jar:2.8.9:compile
[INFO] |  +- org.springframework:spring-web:jar:4.3.10.RELEASE:compile
[INFO] |  |  +- org.springframework:spring-aop:jar:4.3.10.RELEASE:compile
[INFO] |  |  +- org.springframework:spring-beans:jar:4.3.10.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-context:jar:4.3.10.RELEASE:compile
[INFO] |  \- org.springframework:spring-webmvc:jar:4.3.10.RELEASE:compile
[INFO] |     \- org.springframework:spring-expression:jar:4.3.10.RELEASE:compile
[INFO] +- org.springframework.boot:spring-boot-starter-test:jar:1.5.6.RELEASE:test
[INFO] |  +- org.springframework.boot:spring-boot-test:jar:1.5.6.RELEASE:test
[INFO] |  +- org.springframework.boot:spring-boot-test-autoconfigure:jar:1.5.6.RELEASE:test
[INFO] |  +- junit:junit:jar:4.12:test
[INFO] |  +- org.assertj:assertj-core:jar:2.6.0:test
[INFO] |  +- org.mockito:mockito-core:jar:1.10.19:test
[INFO] |  |  \- org.objenesis:objenesis:jar:2.1:test
[INFO] |  +- org.hamcrest:hamcrest-core:jar:1.3:test
[INFO] |  +- org.hamcrest:hamcrest-library:jar:1.3:test
[INFO] |  +- org.skyscreamer:jsonassert:jar:1.4.0:test
[INFO] |  |  \- com.vaadin.external.google:android-json:jar:0.0.20131108.vaadin1:test
[INFO] |  +- org.springframework:spring-core:jar:4.3.10.RELEASE:compile
[INFO] |  \- org.springframework:spring-test:jar:4.3.10.RELEASE:test
[INFO] +- com.jayway.jsonpath:json-path:jar:2.2.0:test
[INFO] |  +- net.minidev:json-smart:jar:2.2.1:test
[INFO] |  |  \- net.minidev:accessors-smart:jar:1.1:test
[INFO] |  |     \- org.ow2.asm:asm:jar:5.0.3:test
[INFO] |  \- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO] +- org.projectlombok:lombok:jar:1.16.20:compile
[INFO] \- log4j:log4j:jar:1.2.17:compile

对于常见的

[INFO] qwerty.project:qwerty.common:jar:0.1
[INFO] +- com.mchange:c3p0:jar:0.9.5.2:compile
[INFO] |  \- com.mchange:mchange-commons-java:jar:0.2.11:compile
[INFO] +- mysql:mysql-connector-java:jar:8.0.12:compile
[INFO] |  \- com.google.protobuf:protobuf-java:jar:2.6.0:compile
[INFO] +- org.projectlombok:lombok:jar:1.16.20:compile
[INFO] \- log4j:log4j:jar:1.2.17:compile

最佳答案

该问题与 Maven 无关。您包含的依赖项根本不包含类com.mysql.cj.jdbc.Driver。您是指 com.mysql.jdbc.Driver 吗？或者您需要更新版本的连接器吗？

--编辑--

好的。刚刚意识到，你有两个不同的版本。所以这是一个Maven问题。 我假设父项目之一管理对旧项目的依赖项版本。

解决方案:将依赖管理放入根 pom 中的预期版本。

关于java - 为什么不解决其他模块的 mysql 依赖关系，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52775822/

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