盡管添加了依賴項，但java.lang.ClassNotFoundException

Question

我的連接管理器類如下：

package com.ideas.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectionManager {

    public Connection getConnection() {
        Connection connection = null ; 


        //next two lines are always same
        try {

            Class.forName("com.mysql.cj.jdbc.Driver");

            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/formsdb", "root", "root");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;

    }
}

我已經為上述課程寫了以下測試：

package com.ideas.db;

import org.junit.Assert;
import org.junit.Test;

public class ConnectionManagerTest {
    @Test
    public void shouldGetConnection(){
        ConnectionManager connectionManager= new ConnectionManager();
        Assert.assertNotNull(connectionManager.getConnection());
    }
}

我在pom.xml文件中添加了以下依賴項：

<dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>6.0.3</version>
    </dependency>

但是，運行測試時我仍然收到錯誤消息

java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
    at java.net.URLClassLoader$1.run(URLClassLoader.java:370)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at com.ideas.db.ConnectionManager.getConnection(ConnectionManager.java:16)
    at com.ideas.db.ConnectionManagerTest.shouldGetConnection(ConnectionManagerTest.java:10)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.util.zip.ZipException: invalid LOC header (bad signature)
    at java.util.zip.ZipFile.read(Native Method)
    at java.util.zip.ZipFile.access$1400(ZipFile.java:61)
    at java.util.zip.ZipFile$ZipFileInputStream.read(ZipFile.java:717)
    at java.util.zip.ZipFile$ZipFileInflaterInputStream.fill(ZipFile.java:420)
    at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:158)
    at java.util.jar.Manifest$FastInputStream.fill(Manifest.java:441)
    at java.util.jar.Manifest$FastInputStream.readLine(Manifest.java:375)
    at java.util.jar.Manifest$FastInputStream.readLine(Manifest.java:409)
    at java.util.jar.Attributes.read(Attributes.java:376)
    at java.util.jar.Manifest.read(Manifest.java:199)
    at java.util.jar.Manifest.<init>(Manifest.java:69)
    at java.util.jar.JarFile.getManifestFromReference(JarFile.java:199)
    at java.util.jar.JarFile.getManifest(JarFile.java:180)
    at sun.misc.URLClassPath$JarLoader$2.getManifest(URLClassPath.java:944)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:450)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
    ... 33 more

Answer 1

看起來MySQL jar文件可能已損壞：

Caused by: java.util.zip.ZipException: invalid LOC header (bad signature)

從本地Maven存儲庫中刪除JAR文件，然后嘗試再次運行Maven。

Answer 2

您的ZIP文件似乎有缺陷。

JAR文件本質上是ZIP文件。 從本地存儲庫中刪除jar文件，然后從依賴項服務器重新加載它。 您還可以使用jar應用程序測試jar文件。

重要的例外是

Caused by: java.util.zip.ZipException: invalid LOC header (bad signature)
    at java.util.zip.ZipFile.read(Native Method)
    at java.util.zip.ZipFile.access$1400(ZipFile.java:61)

這意味着您下載的依賴項無法正確解壓/加載。