类未找到异常 Postgresql。已在 pom 中导入 maven 依赖。

huangapple
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英文:

Class Not Found Exception Postgresql. Already imported maven dependency in pom

问题

错误为：java: 未报告的异常 java.lang.ClassNotFoundException；必须捕获或声明为可抛出，并出现在此处：Class.forName("org.postgresql.Driver");

大多数情况下，这是因为奇怪的Maven格式或类似的问题，但我认为我已经弄对了（复制粘贴）。
以下是 pom.xml 部分内容：

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0"
  3.          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  5.     <modelVersion>4.0.0</modelVersion>
  7.     <groupId>org.example</groupId>
  8.     <artifactId>Database-Test</artifactId>
  9.     <version>1.0-SNAPSHOT</version>
  10.     <packaging>jar</packaging>
  11.     <build>
  12.         <plugins>
  13.             <plugin>
  14.                 <artifactId>maven-assembly-plugin</artifactId>
  15.                 <executions>
  16.                     <execution>
  17.                         <phase>package</phase>
  18.                         <goals>
  19.                             <goal>single</goal>
  20.                         </goals>
  21.                     </execution>
  22.                 </executions>
  23.                 <configuration>
  24.                     <descriptorRefs>
  25.                         <descriptorRef>jar-with-dependencies</descriptorRef>
  26.                     </descriptorRefs>
  27.                 </configuration>
  28.             </plugin>
  29.         </plugins>
  30.     </build>
  31.     <dependencies>
  32.         <dependency>
  33.             <groupId>org.postgresql</groupId>
  34.             <artifactId>postgresql</artifactId>
  35.             <version>9.4-1203-jdbc4</version>
  36.         </dependency>
  37.     </dependencies>
  38. </project>

如果需要，这是文件路径：

类未找到异常 Postgresql。已在 pom 中导入 maven 依赖。

还有主类部分：

  1. import java.net.URI;
  2. import java.net.URISyntaxException;
  3. import java.sql.*;
  5. public class DBTEST{
  6.     public static void main (String[]args) throws SQLException, URISyntaxException{
  7.         System.out.println(getConnection());
  8.     }
  9.     private static Connection getConnection() throws URISyntaxException, SQLException{
  10.         Class.forName("org.postgresql.Driver");
  11.         //String dbUrl = System.getenv("DATABASE_URL");
  12.         String dbUrl = "postgres://fxeymwfokhsimv:bd5c9975533c20ed3ab4df7c0ea263911207854c2cac46983fafce18689a1161@ec2-184-72-162-198.compute-1.amazonaws.com:5432/dlfvrduvj5qcr";
  13.         return DriverManager.getConnection(dbUrl);
  14.     }
  15. }

DB 主机和数据库：

类未找到异常 Postgresql。已在 pom 中导入 maven 依赖。

不要担心我分享我的数据库凭据 - 这只是一个测试项目，只是为了让我弄清楚如何使用它。

英文:

Error is: java: unreported exception java.lang.ClassNotFoundException; must be caught or declared to be thrown and occurs at this: Class.forName(&quot;org.postgresql.Driver&quot;);

Most of the time, it was weird maven formatting or the such, but I think I have it right (copy pasted).
Here is the pom.xml

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  2. &lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot;
  3.          xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
  4.          xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd&quot;&gt;
  5.     &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  7.     &lt;groupId&gt;org.example&lt;/groupId&gt;
  8.     &lt;artifactId&gt;Database-Test&lt;/artifactId&gt;
  9.     &lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
  10.     &lt;packaging&gt;jar&lt;/packaging&gt;
  11.     &lt;build&gt;
  12.         &lt;plugins&gt;
  13.             &lt;plugin&gt;
  14.                 &lt;artifactId&gt;maven-assembly-plugin&lt;/artifactId&gt;
  15.                 &lt;executions&gt;
  16.                     &lt;execution&gt;
  17.                         &lt;phase&gt;package&lt;/phase&gt;
  18.                         &lt;goals&gt;
  19.                             &lt;goal&gt;single&lt;/goal&gt;
  20.                         &lt;/goals&gt;
  21.                     &lt;/execution&gt;
  22.                 &lt;/executions&gt;
  23.                 &lt;configuration&gt;
  24.                     &lt;descriptorRefs&gt;
  25.                         &lt;descriptorRef&gt;jar-with-dependencies&lt;/descriptorRef&gt;
  26.                     &lt;/descriptorRefs&gt;
  27.                 &lt;/configuration&gt;
  28.             &lt;/plugin&gt;
  29.         &lt;/plugins&gt;
  30.     &lt;/build&gt;
  31.     &lt;dependencies&gt;
  32.         &lt;dependency&gt;
  33.             &lt;groupId&gt;org.postgresql&lt;/groupId&gt;
  34.             &lt;artifactId&gt;postgresql&lt;/artifactId&gt;
  35.             &lt;version&gt;9.4-1203-jdbc4&lt;/version&gt;
  36.         &lt;/dependency&gt;
  37.     &lt;/dependencies&gt;
  38. &lt;/project&gt;

If needed, here is the file path
类未找到异常 Postgresql。已在 pom 中导入 maven 依赖。

and the main class

  1. import java.net.URI;
  2. import java.net.URISyntaxException;
  3. import java.sql.*;
  5. public class DBTEST{
  6.     public static void main (String[]args) throws SQLException, URISyntaxException{
  7.         System.out.println(getConnection());
  8.     }
  9.     private static Connection getConnection() throws URISyntaxException, SQLException{
  10.         Class.forName(&quot;org.postgresql.Driver&quot;);
  11.         //String dbUrl = System.getenv(&quot;DATABASE_URL&quot;);
  12.         String dbUrl = &quot;postgres://fxeymwfokhsimv:bd5c9975533c20ed3ab4df7c0ea263911207854c2cac46983fafce18689a1161@ec2-184-72-162-198.compute-1.amazonaws.com:5432/dlfvrduvj5qcr&quot;;
  13.         return DriverManager.getConnection(dbUrl);
  14.     }
  15. }

DB Host and Database类未找到异常 Postgresql。已在 pom 中导入 maven 依赖。
Don't worry about me sharing my database credentials - this is a test project and is just for me to figure out how to use it.

答案1

得分: 0

Maven默认情况下不会将依赖项与jar一起打包，您必须使用插件来完成。请查看此帖子 - https://stackoverflow.com/questions/1729054/including-dependencies-in-a-jar-with-maven

由于您正在使用jdbc 4驱动程序，不需要使用Class.forName。
程序中的错误是由于未处理的ClassNotFoundException（使用Class.forName）和无效的驱动程序URL引起的。

英文:

Maven won't package dependencies with jar by default, you have to do it with the plugin.
Check this thread - https://stackoverflow.com/questions/1729054/including-dependencies-in-a-jar-with-maven

You don't need Class.forName as you are using jdbc 4 driver.
The error in your program is due to unhandled ClassNotFoundException for using Class.forName and invalid driver URL.

huangapple
  • 本文由 发表于 2020年9月9日 00:50:01
  • 转载请务必保留本文链接：https://go.coder-hub.com/63798321.html
  • classnotfoundexception
  • java
  • maven
  • postgresql
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