Spring Boot，JPA 错误：“通过 JDBC 语句执行 DDL 时出错”

我正在尝试使用一个非常基本的（到目前为止）Spring Boot 应用程序在我的 MySQL 数据库中添加一个条目。我使用了在网上找到的一些零碎内容，这是我试图遵循的代码：

netgloo/spring-boot-samples/spring-boot-mysql-springdatajpa-hibernate https://github.com/netgloo/spring-boot-samples/tree/master/spring-boot-mysql-springdatajpa-hibernate

目前，我在运行应用程序时遇到以下问题。

当我第一次运行该应用程序时，会引发以下异常：

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL via JDBC Statement

当我向控制器发出 POST 请求时（该请求应该在数据库中创建一个新条目），我收到以下异常：

org.springframework.orm.jpa.JpaSystemException: could not execute statement; nested exception is org.hibernate.exception.GenericJDBCException: could not execute statement

这又是由以下原因引起的：

Caused by: java.sql.SQLException: No database selected

应用程序属性：

# Web pages extension
spring.mvc.view.suffix =.html

# ==============================
# --- DATA SOURCE
# ==============================

# Database url
spring.datasource.url = jdbc:mysql://localhost:3306?useSSL=false

# Database credentials
spring.datasource.username = root
spring.datasource.password = root

# Keep database connection alive
spring.datasource.tomcat.test-while-idle = true
spring.datasource.tomcat.validation-query = SELECT 1

# ==============================
# --- JPA / Hibernate
# ==============================

# Hibernate ddl auto (create, create-drop, update): with "update" the database
# schema will be automatically updated accordingly to java entities found in
# the project
spring.jpa.hibernate.ddl-auto = update

# Naming strategy
spring.jpa.hibernate.naming.strategy = org.hibernate.cfg.ImprovedNamingStrategy

# Allows Hibernate to generate SQL optimized for a particular DBMS
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>my.group</groupId>
<artifactId>myapp</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>myapp</name>
<description>Demo project for Spring Boot</description>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.8.RELEASE</version>
</parent>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

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

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.2.12.Final</version>
    </dependency>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>5.2.12.Final</version>
    </dependency>


    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20171018</version>
    </dependency>



</dependencies>

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

我有这个简单的界面：

@Transactional
public interface UserDAO extends CrudRepository<User, Long>
{
    public User findByEmail(String email);
}

这是我的控制器：

@Controller
public class UserController
{
    @Autowired
    private UserDAO userDAO;

    @RequestMapping(value = "/register", method = RequestMethod.GET)
    public String getRegisterView()
    {
        return "register/registerView";
    }

    @RequestMapping(value = "/register", method = RequestMethod.POST)
    public @ResponseBody
    ControllerResponse registerRequest(@RequestBody String request)
    {
        User user = null;
        JSONObject json = new JSONObject(request);

        try
        {
            user = new User();

            user.setEmail(json.getString("email"));
            user.setName(json.getString("name"));
            user.setSurname(json.getString("surname"));
            user.setPassword(json.getString("password"));

            userDAO.save(user);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

        ControllerResponse response = new ControllerResponse();
        response.setMessage("Controller returned this");
        response.setSuccess(true);
        return response;
    }
}

我的用户类定义如下：

public class User
{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @NotNull
    private String email;

    @NotNull
    private String password;

    @NotNull
    private String name;

    @NotNull
    private String surname;

    @Column(name = "authorization_token")
    private String authorizationToken;

    // bunch of getters/setters
}

application.properties 中的数据源 URL 缺少数据库名称。应该是这样的。

spring.datasource.url = jdbc:mysql://localhost:3306/dbname?useSSL=false