报错

项目为spingboot项目，打包成了jar包。打包时就发现文件太小，只有200多K，一运行果然报错。

解决

pom.xml中添加

<plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <version>${springboot-version}</version>
        <executions>
          <execution>
            <goals>
              <goal>repackage</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

重新打包，发现jar大小正常了，但是再运行出现了另外一个错（这里是我项目的原因，针对如题错误，到此应该解决了）

报错 unsupportedClassVersionError

1、再次运行还是报错

unsupportedClassVersionError PreView features are not enabled for xxx try running with '--enable-preview'

根据提示，以–enable-preview运行项目，但是还是报错

去掉了pom.xml中enable-preview属性

<plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <encoding>UTF-8</encoding>
          <release>14</release>
          <!--<compilerArgs>--enable-preview</compilerArgs>-->
          <!--idea不重置language level-->
          <source>11</source>
          <target>11</target>
          <!--idea不重置language level-->
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <version>${springboot-version}</version>
        <executions>
          <execution>
            <goals>
              <goal>repackage</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>3.0.0-M5</version>
        <configuration>
          <!--<argLine>--enable-preview</argLine>-->
        </configuration>
      </plugin>

2、打包运行又报错

jdbcTemplate that could not found

去掉了启动类中@SpringBootApplication(exclude= {DataSourceAutoConfiguration.class})
里的(exclude= {DataSourceAutoConfiguration.class})
注：exclude是在服务中不需要访问数据库时添加，如果需要访问则不要添加

又报错

failed to configure a datasource 'url' attributu is not specified and no embedded datasource

添加了resources目录的扫描

<resources>
      <resource>
        <!-- xml放在java目录下-->
        <directory>src/main/java</directory>
        <includes>
          <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
        <includes>
          <include>**/*.yml</include>
          <include>**/*.properties</include>
          <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
      </resource>
    </resources>

运行成功
问题解决