尽管添加了依赖项，但java.lang.ClassNotFoundException

Question

My connection manager class is as follows:

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;

    }
}

and i have written following test for the above class:

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());
    }
}

I have added following dependency in my pom.xml file:

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

However, I am still getting the error when I run the test

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

Looks like the MySQL jar file may corrupted:

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

Delete the JAR file from your local Maven repository and try running Maven again.

Answer 2

Your ZIP file seems defective.

JAR files are essentially ZIP files. Remove the jar file from the local repository and reload it from the dependency server. You can also test the jar file using the jar application.

The essential exception is

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)

This means, your downloaded dependency cannot be properly unpacked/loaded.