记一次mybatis-plus踩坑：NullPointerException:Cannot invoke “String.split(String)“ because “v1“ is null

时间的痕迹01

已于 2024-11-20 08:45:37 修改

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文章标签： mybatis java spring

于 2024-11-19 19:13:31 首次发布

本文链接：https://blog.youkuaiyun.com/qq_17805707/article/details/143892676

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写在前面，其实我个人是很不喜欢用mybatis-plus的，因为我很讨厌在代码里面写sql，或者是用链式编程写sql逻辑，因为很不直观，但是新公司新项目里面用了，也只能硬着头皮用了

今天碰到一个很奇怪的问题，本地idea启动运行完全没问题，maven打完包之后启动就一直报空指针异常，找了一下午，简直要崩溃：

Caused by: java.lang.NullPointerException: Cannot invoke "String.split(String)" because "v1" is null
	at com.github.yulichang.toolkit.VersionUtils.compare(VersionUtils.java:12)
	at com.github.yulichang.injector.MPJSqlInjector.getJoinMethod(MPJSqlInjector.java:117)
	at com.github.yulichang.injector.MPJSqlInjector.methodFilter(MPJSqlInjector.java:111)
	at com.github.yulichang.injector.MPJSqlInjector.getMethodList(MPJSqlInjector.java:93)
	at com.pig4cloud.pigx.common.data.datascope.DataScopeSqlInjector.getMethodList(DataScopeSqlInjector.java:24)
	at com.baomidou.mybatisplus.core.injector.AbstractSqlInjector.inspectInject(AbstractSqlInjector.java:49)
	at com.github.yulichang.injector.MPJSqlInjector.inspectInject(MPJSqlInjector.java:168)
	at com.baomidou.mybatisplus.core.MybatisMapperAnnotationBuilder.parserInjector(MybatisMapperAnnotationBuilder.java:133)
	at com.baomidou.mybatisplus.core.MybatisMapperAnnotationBuilder.parse(MybatisMapperAnnotationBuilder.java:123)
	at com.baomidou.mybatisplus.core.MybatisMapperRegistry.addMapper(MybatisMapperRegistry.java:95)
	at com.baomidou.mybatisplus.core.MybatisConfiguration.addMapper(MybatisConfiguration.java:129)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.bindMapperForNamespace(XMLMapperBuilder.java:445)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:102)
	at com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean.buildSqlSessionFactory(MybatisSqlSessionFactoryBean.java:570)
	... 75 common frames omitted

具体的代码也就是mp源码com.github.yulichang.toolkit.VersionUtils的这里：

    public static int compare(String v1, String v2) {
        String[] v1s = v1.split("\\.");
        String[] v2s = v2.split("\\.");

        String[] vs = v1s.length > v2s.length ? v2s : v1s;
        for (int i = 0; i < vs.length; i++) {
            int compareV = compareV(v1s[i], v2s[i]);
            if (compareV != 0) {
                return compareV;
            }
        }
        if (v1s.length == v2s.length) {
            return 0;
        }
        return v1s.length > v2s.length ? 1 : -1;
    }

调用方在这里：com.github.yulichang.injector.MPJSqlInjector

    public List<AbstractMethod> getMethodList(Class<?> mapperClass) {
        if (VersionUtils.compare(MybatisPlusVersion.getVersion(), "3.4.3.2") >= 0) {
            throw ExceptionUtils.mpe("DefaultSqlInjector 的 getMethodList(Class<?> mapperClass) 方法已在 3.4.3.2+ 改为" +
                    "getMethodList(Class<?> mapperClass, TableInfo tableInfo)\n");
        }
        if (Objects.nonNull(sqlInjector)) {
            List<AbstractMethod> methodList = AbstractMethodV3431.getMethod(sqlInjector, mapperClass);
            return methodFilter(methodList);
        } else {
            List<AbstractMethod> list = Stream.of(
                    new Insert(),
                    new DeleteByMap(),
                    new DeleteById(),
                    new DeleteBatchByIds(),
                    new UpdateById(),
                    new SelectById(),
                    new SelectBatchByIds(),
                    new SelectByMap()
            ).collect(toList());
            list.addAll(getWrapperMethod());
            list.addAll(getJoinMethod());
            return list;
        }
    }

也就是说MybatisPlusVersion.getVersion()返回的是null，进去这个方法里面去看:

    public static String getVersion() {
        return determineSpringBootVersion();
    }

    private static String determineSpringBootVersion() {
        final Package pkg = MybatisPlusVersion.class.getPackage();
        if (pkg != null && pkg.getImplementationVersion() != null) {
            return pkg.getImplementationVersion();
        }
        CodeSource codeSource = MybatisPlusVersion.class.getProtectionDomain().getCodeSource();
        if (codeSource == null) {
            return null;
        }
        URL codeSourceLocation = codeSource.getLocation();
        try {
            URLConnection connection = codeSourceLocation.openConnection();
            if (connection instanceof JarURLConnection) {
                return getImplementationVersion(((JarURLConnection) connection).getJarFile());
            }
            try (JarFile jarFile = new JarFile(new File(codeSourceLocation.toURI()))) {
                return getImplementationVersion(jarFile);
            }
        } catch (Exception ex) {
            return null;
        }
    }

    private static String getImplementationVersion(JarFile jarFile) throws IOException {
        return jarFile.getManifest().getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_VERSION);
    }

也就是最终会调用private static String getImplementationVersion(JarFile jarFile)这个方法，刚开始没注意，以为这个就是正常的读取jar里面的内容，于是各种百度，AI大模型，在偶然的情况下改了一下pom文件里面的打包配置，也就是加了下面这个插件：

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.1.0</version>
            <configuration>
                <archive>
                    <manifestEntries>
                        <Implementation-Version>${project.version}</Implementation-Version>
                    </manifestEntries>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

莫名奇妙就好了（原本是没有加这个插件的，并且我的项目是java代码和scala代码混在一个项目里面写的），后面问了一下chatgpt这个getImplementationVersion是干嘛的，它是这么说的：

于是点进去源码里面看，是jdk源码里面读取jar的，最核心的代码就在这里了，图中标红的地方相信大家都不陌生，用maven编译打包都会生成这个文件：

这个文件的内容如下：

Manifest-Version: 1.0
Created-By: Apache Maven 3.9.2
Built-By: Administrator
Build-Jdk: 17.0.9
Implementation-Version: 5.3.0
Main-Class: org.springframework.boot.loader.JarLauncher
Start-Class: com.das.geo.GeotrellisApplication
Spring-Boot-Version: 2.7.18
Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/
Spring-Boot-Classpath-Index: BOOT-INF/classpath.idx
Spring-Boot-Layers-Index: BOOT-INF/layers.idx

里面的Implementation-Version也正是pom文件里面配置的maven-jar-plugin这个插件配置的：

下面是最终完整的插件配置：搞不懂为什么mybatis-plus要读这个配置，坑了我一下午

<plugins>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>4.5.4</version>
                <executions>
                    <execution>
                        <id>scala-compile-first</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>add-source</goal>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <scalaVersion>${scala.version}</scalaVersion>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.1.0</version>
                <configuration>
                    <archive>
                        <manifestEntries>
                            <Implementation-Version>${project.version}</Implementation-Version>
                        </manifestEntries>
                    </archive>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring-boot.version}</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>com.github.therapi</groupId>
                            <artifactId>therapi-runtime-javadoc-scribe</artifactId>
                            <version>0.15.0</version>
                        </path>
                    </annotationProcessorPaths>
                    <encoding>UTF-8</encoding>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                    <compilerArgument>-Xlint:unchecked</compilerArgument>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.3.0</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                </transformer>
                            </transformers>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <finalName>${project.build.finalName}</finalName> <!-- 指定生成的 JAR 文件名 -->
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>