如何解决mvn clean install“NullPointerException”错误？

问题描述 投票：0回答：1

我是新手。几天来我一直在尝试解决这个问题。我有一个 Spring 启动 Java 代码。在这个项目中，有一个我在项目中使用的cholSolver.jar。 jar文件在项目路径中，但我也使用

mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> -DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>
安装了它。我将其添加到 pom.xml 文件中。 pom.xml 文件：

<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>3.1.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo1</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>20</java.version>
   </properties>

   
 
    <dependencies>
        <dependency>
            <groupId>com.googlecode.matrix-toolkits-java</groupId>
            <artifactId>mtj</artifactId>
            <version>1.0.2</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.example</groupId>
    <artifactId>javabuilder</artifactId>
    <version>R2023a</version>
</dependency>


    <dependency>
        <groupId>com.example</groupId>
        <artifactId>cholSolver</artifactId>
        <version>1.0.0</version>
    </dependency>
 

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>   
    
</project>

在安装 jar 文件之前，我还尝试使用 

<scope>system</scope>
添加它。像这样：

  <dependency>
        <groupId>peridynamics</groupId>
        <artifactId>cholSolver</artifactId>
        <version>1.0</version>
        <scope>system</scope>
        <systemPath>${cholSolver.path}</systemPath>
    </dependency>    
    <dependency>
        <groupId>com.mathworks</groupId>
        <artifactId>javabuilder</artifactId>
        <version>R2023a</version>
        <scope>system</scope>
        <systemPath>${javabuilder.path}</systemPath>
    </dependency>

我在添加依赖项时注意了它们的版本和名称。无论我在哪里进行研究，都建议这个（范围）不是一个好主意，并且应该将其安装在 mvn 存储库中。不管怎样，我的问题还没有解决。出于隐私原因，我无法共享代码，但我可以展示如何在如下部分中使用 cholSolver：

import cholSolver.Cholmod2;

Cholmod2 cholSolver;

try {
    cholSolver = new Cholmod2();
} catch (MWException e) {
    e.printStackTrace();
}

mvn测试结果：

-------------------------------------------------------------------------------
Test set: peridynamics.demoAppTests
-------------------------------------------------------------------------------
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 2.38 s <<< FAILURE! - in peridynamics.demoAppTests
peridynamics.demoAppTests.contextLoads  Time elapsed: 0.008 s  <<< ERROR!
java.lang.IllegalStateException: Failed to load ApplicationContext for [WebMergedContextConfiguration@a92be4f testClass = peridynamics.demoAppTests, locations = [], classes = [peridynamics.demoApp], contextInitializerClasses = [], activeProfiles = [], propertySourceLocations = [], propertySourceProperties = ["org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true"], contextCustomizers = [org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@312aa7c, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@5a59ca5e, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@2a8448fa, org.springframework.boot.test.autoconfigure.actuate.observability.ObservabilityContextCustomizerFactory$DisableObservabilityContextCustomizer@1f, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@5884a914, org.springframework.boot.test.context.SpringBootTestAnnotation@23729b12], resourceBasePath = "src/main/webapp", contextLoader = org.springframework.boot.test.context.SpringBootContextLoader, parent = null]
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:143)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:127)
    at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:191)
    at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:130)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:241)
    at org.springframework.test.context.junit.jupiter.SpringExtension.postProcessTestInstance(SpringExtension.java:138)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$10(ClassBasedTestDescriptor.java:377)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.executeAndMaskThrowable(ClassBasedTestDescriptor.java:382)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$11(ClassBasedTestDescriptor.java:377)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
    at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179)
    at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
    at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:310)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:735)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:734)
    at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:762)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstancePostProcessors(ClassBasedTestDescriptor.java:376)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$instantiateAndPostProcessTestInstance$6(ClassBasedTestDescriptor.java:289)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:288)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$4(ClassBasedTestDescriptor.java:278)
    at java.base/java.util.Optional.orElseGet(Optional.java:364)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$5(ClassBasedTestDescriptor.java:277)
    at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:31)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:105)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:104)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:68)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$2(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:90)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:147)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:127)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:90)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:55)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:102)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.apache.maven.surefire.junitplatform.LazyLauncher.execute(LazyLauncher.java:50)
    at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.execute(JUnitPlatformProvider.java:184)
    at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invokeAllTests(JUnitPlatformProvider.java:148)
    at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invoke(JUnitPlatformProvider.java:122)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:385)
    at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:162)
    at org.apache.maven.surefire.booter.ForkedBooter.run(ForkedBooter.java:507)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:495)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'beso3D_PD' defined in file [C:\Users\suuser\Desktop\PDTO-GitHub\PDTO-Project\pdtopolys\fea\target\classes\peridynamics\Beso3D_PD.class]: Failed to instantiate [peridynamics.Beso3D_PD]: Constructor threw exception
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1314)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1199)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:560)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:520)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:973)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:942)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:608)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:436)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:312)
    at org.springframework.boot.test.context.SpringBootContextLoader.lambda$loadContext$3(SpringBootContextLoader.java:137)
    at org.springframework.util.function.ThrowingSupplier.get(ThrowingSupplier.java:58)
    at org.springframework.util.function.ThrowingSupplier.get(ThrowingSupplier.java:46)
    at org.springframework.boot.SpringApplication.withHook(SpringApplication.java:1406)
    at org.springframework.boot.test.context.SpringBootContextLoader$ContextLoaderHook.run(SpringBootContextLoader.java:545)
    at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:137)
    at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:108)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:187)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:119)
    ... 73 more
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [peridynamics.Beso3D_PD]: Constructor threw exception
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:224)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:87)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1308)
    ... 95 more
Caused by: java.lang.NullPointerException: Cannot invoke "cholSolver.Cholmod2.cholSolver(Object[], Object[])" because "this.cholSolver" is null
    at peridynamics.Beso3D_PD.solve(Beso3D_PD.java:749)
    at peridynamics.Beso3D_PD.run(Beso3D_PD.java:668)
    at peridynamics.Beso3D_PD.<init>(Beso3D_PD.java:149)
    at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:67)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:484)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:198)
    ... 97 more

我不知道为什么 cholSolver 返回 null 并抛出 NullPointerException 错误。我什至不确定你是否正确读取了 jar 文件。我怎么解决这个问题？预先感谢您。

java spring spring-boot maven nullpointerexception
1个回答
0
投票

错误消息显示您的 

cholSolver
实例变量是 
null
。 这可能意味着当您尝试实例化 
MWException
类时会抛出 
Cholmod2
，但您选择忽略该异常并仅打印其堆栈跟踪。

将 

e.printStackTrace()
替换为：

throw new IllegalStateException(e);

因此，如果

cholSolver
无法初始化，您的程序将会崩溃，而不是继续稍后崩溃并隐藏真正的原因。

即使在当前输出中，您也应该能够在故障上方的某处看到根本原因的原始堆栈跟踪。

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