不兼容的类型：java.util.Optional<xyz.app.entity.Users> 无法转换为用户(Springboot 编译错误)

Question

我在 Spring 引导应用程序中的以下行收到不兼容的类型错误消息：

RequestDO request = requestRepository.findOne(requestModel.getRequestId());
Users employee = usersRepository.findOne(request.getUsers().getId());

我以前没有在这种情况下遇到过此错误。我的应用自大约一个月前首次生产版本以来一直成功运行。

构建失败：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project tmt: Compilation failure: Compilation failure:
[ERROR] /C:/Users/martin/Documents/Web Projects/home.office/src/main/java/xyz/app/controller/UserController.java:[45,45] incompatible types: java.util.Optional<xyz.app.entity.Users> cannot be converted to xyz.app.entity.Users
[ERROR] /C:/Users/martin/Documents/Web Projects/home.office/src/main/java/xyz/app/controller/RequestController.java:[139,54] incompatible types: java.util.Optional<xyz.app.entity.RequestDO> cannot be converted to xyz.app.entity.RequestDO
[ERROR] /C:/Users/martin/Documents/Web Projects/home.office/src/main/java/xyz/app/controller/RequestController.java:[140,49] incompatible types: java.util.app<xyz.app.entity.Users> cannot be converted to xyz.app.entity.Users
[ERROR] /C:/Users/martin/Documents/Web Projects/home.office/src/main/java/xyz/app/controller/RequestController.java:[155,54] incompatible types: java.util.Optional<v.app.entity.RequestDO> cannot be converted to xyz.app.entity.RequestDO
[ERROR] /C:/Users/martin/Documents/Web Projects/home.office/src/main/java/xyz/app/controller/RequestController.java:[157,49] incompatible types: java.util.Optional<xyz.app.entity.Users> cannot be converted to xyz.app.entity.Users

自从上次成功重建项目以来，我没有进行任何代码更改。这让我相信 springframework Maven 依赖项最近发生了变化，导致我的代码中断。是否可以通过在我的pom.xml中恢复到较旧的快照来测试这一点？另外，可能导致错误的原因是什么？

聚 甲醛

<?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>xyz.app</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>app</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.BUILD-SNAPSHOT</version>
        <relativePath/>
        <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.microsoft.sqlserver</groupId>
            <artifactId>sqljdbc4</artifactId>
            <version>4.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <!--<dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc7</artifactId>
            <version>12.1.0.1</version>
        </dependency>-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-ldap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.directory.server</groupId>
            <artifactId>apacheds-server-jndi</artifactId>
            <version>1.5.5</version>
        </dependency>
        <dependency>
            <groupId>it.ozimov</groupId>
            <artifactId>spring-boot-email-core</artifactId>
            <version>0.4.0</version>
        </dependency>
        <dependency>
            <groupId>it.ozimov</groupId>
            <artifactId>spring-boot-freemarker-email</artifactId>
            <version>0.4.0</version>
        </dependency>
        <dependency>
            <groupId>org.thymeleaf.extras</groupId>
            <artifactId>thymeleaf-extras-springsecurity4</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>
</project>

Answer 1

我在使用 2.0.0.BUILD-SNAPSHOT 时遇到了类似的问题，所以除非您正在尝试一些低级的 Spring 启动功能，否则请将版本更改为 1.5.2.RELEASE

Answer 2

我遇到了类似的问题，但我仍然没有得到答案。但是有一个解决方案。也许对你有帮助。

不再支持源选项 5