无法使用Spring Boot创建一个mysql数据库

Question

我试图在没有像h2和derby这样的嵌入式数据库的情况下实现Spring Boot，而是使用mysql。我一直收到未知的数据库错误。

pom.hml：

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.2.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</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-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!--        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
    </dependency>-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

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

application.properties:

#Database Configuration
spring.datasource.url=jdbc:mysql://localhost:3306/sampleDB
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.jpa.generate-ddl=true
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

错误：

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown database 'sampledb'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_111]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_111]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_111]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.Util.getInstance(Util.java:387) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:939) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:871) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1694) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1215) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2255) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2286) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2085) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:795) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44) ~[mysql-connector-java-5.1.38.jar:5.1.38]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_111]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_111]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_111]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404) ~[mysql-connector-java-5.1.38.jar:5.1.38]

如果我使用像h2这样的嵌入式数据库，那么它在没有application.properties文件中提到的任何内容的情况下工作，但是如果我使用MySQL，我会收到此错误。请帮忙。

Answer 1

连接到数据库sampleDB，与h2相比，它不是由mysql自动创建的。

你必须使用mysql -u <user> -p -e "create database sampleDB"自己创建它

Answer 2

Spring Boot和Hibernate都不会创建数据库而不是你。

下面的设置只创建表并期望该DB已存在：

spring.jpa.hibernate.ddl-AUTO =创建

但是，当您使用嵌入式数据库（HSQLDB，H2 ...）时，将自动创建数据库。这是供应商特定的行为。

对于MySQL，您可以使用以下配置自动创建DB：

spring.datasource.url =的jdbc：mysql的：//本地主机：3306 / SAMPLEDB createDatabaseIfNotExist =真

注意连接参数。

在这种情况下，数据库将在连接期间自动创建。

Answer 3

您需要先创建数据库。