为什么即使JUnit4在我的有效pom.xml中也不能识别JUnit4导入？

Question

我的Eclipse项目中出现了如下构建错误：

import static org.junit.Assert.assertEquals;

The import org.junit.Assert cannot be resolved

但是如果您看到了有效的pom.xml，那么JUnit4依赖项就存在了：

  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13</version>
  </dependency>

如果将此依赖项显式添加到pom.xml中，则错误将消失。

为什么会这样呢？如果它已经在那里，不应该使用它吗？

这是我的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 https://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>2.3.3.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.product</groupId>
    <artifactId>test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>Test</name>
    <description>Project</description>

    <properties>
        <java.version>8</java.version>
        <azure.version>2.3.3</azure.version>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->

        <!-- https://mvnrepository.com/artifact/de.flapdoodle.embed/de.flapdoodle.embed.mongo -->
        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>

            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson</artifactId>
            <version>3.14.1</version>
        </dependency>
        <!-- -->

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>

        </dependency>

        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>spring-starter-azure-storage</artifactId>
            <version>1.2.8</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>

        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>

            <scope>provided</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.hibernate.javax.persistence/hibernate-jpa-2.1-api -->
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.1-api</artifactId>
            <version>1.0.2.Final</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.modelmapper/modelmapper -->
        <dependency>
            <groupId>org.modelmapper</groupId>
            <artifactId>modelmapper</artifactId>
            <version>2.3.8</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>azure-spring-boot-starter</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/commons-beanutils/commons-beanutils -->
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.4</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.persistence/persistence-api -->
        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>persistence-api</artifactId>
            <version>1.0.2</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.integration/spring-integration-core -->
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-core</artifactId>
        </dependency>
        <!--<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-rest</artifactId> 
            </dependency> -->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-mongodb</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.querydsl/querydsl-mongodb -->
        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-mongodb</artifactId>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.querydsl/querydsl-apt -->
        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-apt</artifactId>
            <!--<version>4.3.1</version> -->
        </dependency>

        <dependency>
            <groupId>commons-codec</groupId>
            <artifactId>commons-codec</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>applicationinsights-spring-boot-starter</artifactId>
            <version>2.5.0</version>
        </dependency>

        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>applicationinsights-logging-logback</artifactId>
            <version>2.5.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        
        <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-api -->
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <!-- ID generator repo setup -->
    <repositories>
        <repository>
            <id>gitlab-maven</id>
            <url>https://gitlab.com/api/v4/projects/22715350/packages/maven</url>
        </repository>
    </repositories>
    <distributionManagement>
        <repository>
            <id>gitlab-maven</id>
            <url>https://gitlab.com/api/v4/projects/22715350/packages/maven</url>
        </repository>
        <snapshotRepository>
            <id>gitlab-maven</id>
            <url>https://gitlab.com/api/v4/projects/22715350/packages/maven</url>
        </snapshotRepository>
    </distributionManagement>


    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.microsoft.azure</groupId>
                <artifactId>azure-spring-boot-bom</artifactId>
                <version>${azure.version}</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>
            <plugin>
                <groupId>com.mysema.maven</groupId>
                <artifactId>apt-maven-plugin</artifactId>
                <version>1.1.3</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>process</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${project.build.directory}/generated-sources/java</outputDirectory>
                            <processor>
                                org.springframework.data.mongodb.repository.support.MongoAnnotationProcessor
                            </processor>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

您提到的依赖项在dependencymanagement中，而不在依赖项中。这意味着您必须简单地编写依赖项，但没有版本（将由spring引导父级控制），当然，您必须添加范围：测试，如下所示：

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <scope>test</scope>
</dependency>

Answer 2

spring boot使用的是JUnit5，这是因为：

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
</dependency>

如果您仍然希望使用JUnit4，则可能希望删除排除。