java - Spring Data java 配置找不到 org.postgresql.Driver

Question

我有一个基于 Spring Framework 的项目，它仅基于 Java 配置进行初始化。

使用的技术:

• Java 8
• Spring 框架 4.2.1.RELEASE
• Hibernate ORM 5.0.4.Final
• Spring 工具套件 IDE 3.6.2
• 行家 3
• Tomcat 7

pom.xml....

 <dependencies>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            <exclusions>
                <!-- Exclude Commons Logging in favor of SLF4j -->
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-commons-core</artifactId>
            <version>1.4.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-rest-core</artifactId>
            <version>2.4.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>1.9.1.RELEASE</version>
        </dependency>

        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>

        <!-- Annotations -->
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-jaxb-annotations</artifactId>
            <version>2.6.3</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.6.3</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.6.3</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.6.3</version>
        </dependency>

        <!-- Postgres -->
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>9.4-1205-jdbc42</version>
        </dependency>

        <!-- MySQL Connector -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.37</version>
        </dependency>

        <!-- Hibernate -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.0.4.Final</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.1-api</artifactId>
            <version>1.0.0.Final</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>4.3.1.Final</version>
        </dependency>

        <!-- Transaction -->
        <dependency>
            <groupId>javax.transaction</groupId>
            <artifactId>jta</artifactId>
            <version>1.1</version>
        </dependency>

        <!-- @Inject -->
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

    </dependencies>

....

数据库配置文件

我创建了以下配置类。

而 SystemSettings 保存数据库的用户名、密码和 url

@Service
@Configuration
public class SystemSettings implements Settings {  

    public static final String DS_URL = "datasource.app.url";
    public static final String DS_USERNAME = "datasource.app.username";
    public static final String DS_PASSWORD = "datasource.app.password";

    @Autowired
    private Environment env;

    @Override
    public String get(String key) {
        return env.getProperty(key);
    }

}

值是从 application.properties 文件中提取的，因为它在 PersistenceContext 类中表示。

持久化上下文

@Component
@EnableTransactionManagement
@PropertySource("classpath:application.properties")
public class PersistenceContext {

    @Autowired
    private Environment env;

    @Bean
    @Primary
    public DataSource dataSource() throws ClassNotFoundException {
        org.apache.tomcat.jdbc.pool.DataSource ds = new org.apache.tomcat.jdbc.pool.DataSource();

        String url = env.getProperty(SystemSettings.DS_URL);
        String user = env.getProperty(SystemSettings.DS_USERNAME);
        String pass = env.getProperty(SystemSettings.DS_PASSWORD);

        ds.setDriverClassName("org.postgresql.Driver");
        ds.setUrl(url);
        ds.setUsername(user);
        ds.setPassword(pass);

        return ds;
    }

    @Bean
    LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
        LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactoryBean.setDataSource(dataSource);
        entityManagerFactoryBean.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        entityManagerFactoryBean.setPackagesToScan("com.project.app.services.entities");

        Properties jpaProperties = new Properties();

        // Configures the used database dialect. This allows Hibernate to create SQL
        // that is optimized for the used database.
        jpaProperties.put("hibernate.dialect", env.getRequiredProperty("hibernate.dialect"));

        // Specifies the action that is invoked to the database when the Hibernate
        // SessionFactory is created or closed.
        jpaProperties.put("hibernate.hbm2ddl.auto",
                env.getRequiredProperty("hibernate.hbm2ddl.auto"));  

        // If the value of this property is true, Hibernate writes all SQL
        // statements to the console.
        jpaProperties.put("hibernate.show_sql", env.getRequiredProperty("hibernate.show_sql"));

        // If the value of this property is true, Hibernate will format the SQL
        // that is written to the console.
        jpaProperties.put("hibernate.format_sql", env.getRequiredProperty("hibernate.format_sql"));

        entityManagerFactoryBean.setJpaProperties(jpaProperties);

        return entityManagerFactoryBean;
    }

    @Bean
    JpaTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(entityManagerFactory);
        return transactionManager;
    }
}

还有属性文件

hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect
hibernate.hbm2ddl.auto=create-drop hibernate.show_sql=false
hibernate.format_sql=true

datasource.app.type=POSTGRESQL
datasource.app.driverClassName=org.postgresql.Driver
datasource.app.url=jdbc:postgresql://localhost:5432/app
datasource.app.username=user
datasource.app.password=pass

不幸的是现在我得到了这个错误

SEVERE: Unable to create initial connections of pool. java.sql.SQLException: org.postgresql.Driver at ...... Caused by: java.lang.ClassNotFoundException: org.postgresql.Driver at......

我不知道为什么它给我这个异常(exception)。 Maven 依赖项在那里，驱动程序也在类路径中。 .有什么帮助吗？

这是我项目的结构。您可以看到在构建路径中添加的库。正如评论中所建议的，问题可能是 postgres jar 不在 tomcat 库中。我如何在那里添加它？

Answer 1

我怀疑您有继承类加载器问题，其中 JDBC 驱动程序对您的应用程序可见，但对 Tomcat 的连接池不可见。

参见:

• Why must the JDBC driver be put in TOMCAT_HOME/lib folder?
• https://www.mulesoft.com/tcat/tomcat-jdbc