“无法配置数据源：未指定‘url’属性，无法配置嵌入式数据源”是什么意思。 意思？

Question

所以我正在构建这个 Spring MVC 应用程序，它使用 Hibernate 和 C3P0 连接到 MySQL 数据库，具有以下依赖关系：

<?xml version="1.0" encoding="UTF-8"?>
<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>2.2.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.airlines</groupId>
    <artifactId>Airlines</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Airlines</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <!-- Spring MVC Dependency -->

        <!-- Hibernate ORM -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.2.11.Final</version>
        </dependency>
        <!-- Hibernate-C3P0 Integration -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-c3p0</artifactId>
            <version>5.2.11.Final</version>
        </dependency>
        <!-- c3p0 -->
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.2</version>
        </dependency>
        <!-- Mysql Connector -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.5</version>
        </dependency>
        <!-- Jackson API for JSON -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.8.7</version>
        </dependency>
        <!-- Servlet Dependency -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web-services</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

    </dependencies>

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

</project>

我通过创建一个名为 db.properties 的单独属性文件来构建它：

# MySQL properties
mysql.driver=com.mysql.cj.jdbc.Driver
mysql.url=jdbc:mysql://localhost:3306/airlines
mysql.user=root
mysql.password=

# Hibernate properties
hibernate.show_sql=true
hibernate.hbm2ddl.auto=update

#C3P0 properties
hibernate.c3p0.min_size=5
hibernate.c3p0.max_size=20
hibernate.c3p0.acquire_increment=1
hibernate.c3p0.timeout=1800
hibernate.c3p0.max_statements=150

我正在通过一个名为 AppConfig.java 的 Java class 导入这些设置：

package com.airlines.config;

import java.util.Properties;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.ComponentScans;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.orm.hibernate5.HibernateTransactionManager;
import org.springframework.orm.hibernate5.LocalSessionFactoryBean;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import static org.hibernate.cfg.Environment.*;

@Configuration
@PropertySource("classpath:db.properties")
@EnableTransactionManagement
@ComponentScans(value = { @ComponentScan("com.airlines.dao"),
        @ComponentScan("com.airlines.service") })
public class AppConfig {

    @Autowired
    private Environment env;

    @Bean
    public LocalSessionFactoryBean getSessionFactory() {
        LocalSessionFactoryBean factoryBean = new LocalSessionFactoryBean();

        Properties props = new Properties();
        // Setting JDBC properties
        props.put(DRIVER, env.getProperty("mysql.driver"));
        props.put(URL, env.getProperty("mysql.url"));
        props.put(USER, env.getProperty("mysql.user"));
        props.put(PASS, env.getProperty("mysql.password"));

        // Setting Hibernate properties
        props.put(SHOW_SQL, env.getProperty("hibernate.show_sql"));
        props.put(HBM2DDL_AUTO, env.getProperty("hibernate.hbm2ddl.auto"));

        // Setting C3P0 properties
        props.put(C3P0_MIN_SIZE, env.getProperty("hibernate.c3p0.min_size"));
        props.put(C3P0_MAX_SIZE, env.getProperty("hibernate.c3p0.max_size"));
        props.put(C3P0_ACQUIRE_INCREMENT,
                env.getProperty("hibernate.c3p0.acquire_increment"));
        props.put(C3P0_TIMEOUT, env.getProperty("hibernate.c3p0.timeout"));
        props.put(C3P0_MAX_STATEMENTS, env.getProperty("hibernate.c3p0.max_statements"));

        factoryBean.setHibernateProperties(props);
        factoryBean.setPackagesToScan("com.bushansirgur.model");

        return factoryBean;
    }

    @Bean
    public HibernateTransactionManager getTransactionManager() {
        HibernateTransactionManager transactionManager = new HibernateTransactionManager();
        transactionManager.setSessionFactory(getSessionFactory().getObject());
        return transactionManager;
    }
}

但是，当我运行该应用程序时，出现以下错误：

---

应用程序启动失败

---

描述：

无法配置数据源：未指定“url”属性，无法配置嵌入式数据源。

原因：无法确定合适的驱动程序 class

行动：

请考虑以下几点： 如果您需要嵌入式数据库（H2、HSQL 或 Derby），请将其放在类路径中。 如果您有要从特定配置文件加载的数据库设置，您可能需要激活它（当前没有配置文件处于活动状态）。

有任何想法吗？

Answer 1

设置 SessionFactory 使用的数据源，而不是在 hibernate 设置中定义连接提供程序。

@Bean
    public LocalSessionFactoryBean sessionFactory() {
        LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
        sessionFactory.setDataSource(dataSource());
        sessionFactory.setPackagesToScan("com.bushansirgur.model" );
        sessionFactory.setHibernateProperties(hibernateProperties());
        return sessionFactory;
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(env.getProperty("mysql.driver"));
        dataSource.setUrl(env.getProperty("mysql.jdbcUrl"));
        dataSource.setUsername(env.getProperty("mysql.username"));
        dataSource.setPassword(env.getProperty("mysql.password"));
        return dataSource;
    }

    private Properties hibernateProperties() {
        Properties properties = new Properties();
        properties.put("hibernate.dialect", env.getProperty("hibernate.dialect"));
        properties.put("hibernate.show_sql", env.getProperty("hibernate.show_sql"));
        properties.put(FORMAT_SQL, "true");
        properties.put("hibernate.hbm2ddl.auto", "update");
        // Setting C3P0 properties
        properties.put(C3P0_MIN_SIZE, env.getProperty("hibernate.c3p0.min_size"));
        properties.put(C3P0_MAX_SIZE, env.getProperty("hibernate.c3p0.max_size"));
        properties.put(C3P0_ACQUIRE_INCREMENT, env.getProperty("hibernate.c3p0.acquire_increment"));
        properties.put(C3P0_TIMEOUT, env.getProperty("hibernate.c3p0.timeout"));
        properties.put(C3P0_MAX_STATEMENTS, env.getProperty("hibernate.c3p0.max_statements"));
        return properties;
    }