SpringBootの--Caused by:java.lang.IllegalArgumentException: At least one JPA metamodel must be prese

転載は出典を明記してください.https://blog.csdn.net/l1028386804/article/details/80957448
JPAの構成クラスに次の構成情報を追加する必要があります.

@Bean
public DataSource dataSource() {
    DriverManagerDataSource dataSource = new DriverManagerDataSource();
    dataSource.setDriverClassName("com.mysql.jdbc.Driver");
    dataSource.setUrl("jdbc:mysql://localhost:3306/test?characterEncoding=utf8");
    dataSource.setUsername("root");
    dataSource.setPassword("root");

    return dataSource;
}

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
    LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
    entityManagerFactoryBean.setDataSource(dataSource());
    entityManagerFactoryBean.setPackagesToScan("dbdemo.mysql.entity");
    entityManagerFactoryBean.setJpaProperties(buildHibernateProperties());
    entityManagerFactoryBean.setJpaVendorAdapter(new HibernateJpaVendorAdapter() {{
        setDatabase(Database.MYSQL);
    }});
    return entityManagerFactoryBean;
}

protected Properties buildHibernateProperties() {
    Properties hibernateProperties = new Properties();

    hibernateProperties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
    hibernateProperties.setProperty("hibernate.show_sql", "true");
    hibernateProperties.setProperty("hibernate.use_sql_comments", "false");
    hibernateProperties.setProperty("hibernate.format_sql", "true");
    hibernateProperties.setProperty("hibernate.hbm2ddl.auto", "update");
    hibernateProperties.setProperty("hibernate.generate_statistics", "false");
    hibernateProperties.setProperty("javax.persistence.validation.mode", "none");

    //Audit History flags
    hibernateProperties.setProperty("org.hibernate.envers.store_data_at_delete", "true");
    hibernateProperties.setProperty("org.hibernate.envers.global_with_modified_flag", "true");

    return hibernateProperties;
}

@Bean
public PlatformTransactionManager transactionManager() {
    return new JpaTransactionManager();
}

@Bean
public TransactionTemplate transactionTemplate() {
    return new TransactionTemplate(transactionManager());
}

例えば、従来のJPA構成類は以下の通りである.

package com.lyz.springboot.db.mysql.config;

import org.springframework.boot.orm.jpa.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;


/**
 *  @author liuyazhuang
 *  @description : JPA   
 *  @date: 2018/7/8.
 *
 */
@Order(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@EnableTransactionManagement(proxyTargetClass = true)
@EnableJpaRepositories(basePackages = "com.lyz.**.dao")
@EntityScan(basePackages = "com.lyz.**.entity")

public class JpaConfiguration {
    @Bean
    PersistenceExceptionTranslationPostProcessor persistenceExceptionTranslationPostProcessor(){
        return new PersistenceExceptionTranslationPostProcessor();
    }
}

SpringBootプログラムを実行するとCaused by:javaが表示されます.lang.IllegalArgumentException:At least one JPA metamodel must be preseの異常.
では、この構成クラスに関連する構成方法を追加します.追加されたクラスは次のようになります.

package com.lyz.springboot.db.mysql.config;

import org.springframework.boot.orm.jpa.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.Database;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.transaction.support.TransactionTemplate;

import javax.sql.DataSource;
import java.util.Properties;


/**
 *  @author liuyazhuang
 *  @description : JPA   
 *  @date: 2018/7/8.
 *
 */
@Order(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@EnableTransactionManagement(proxyTargetClass = true)
@EnableJpaRepositories(basePackages = "com.lyz.**.dao")
@EntityScan(basePackages = "com.lyz.**.entity")

public class JpaConfiguration {
    @Bean
    PersistenceExceptionTranslationPostProcessor persistenceExceptionTranslationPostProcessor(){
        return new PersistenceExceptionTranslationPostProcessor();
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/test?characterEncoding=utf8");
        dataSource.setUsername("root");
        dataSource.setPassword("root");

        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactoryBean.setDataSource(dataSource());
        entityManagerFactoryBean.setPackagesToScan("dbdemo.mysql.entity");
        entityManagerFactoryBean.setJpaProperties(buildHibernateProperties());
        entityManagerFactoryBean.setJpaVendorAdapter(new HibernateJpaVendorAdapter() {{
            setDatabase(Database.MYSQL);
        }});
        return entityManagerFactoryBean;
    }

    protected Properties buildHibernateProperties() {
        Properties hibernateProperties = new Properties();

        hibernateProperties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
        hibernateProperties.setProperty("hibernate.show_sql", "true");
        hibernateProperties.setProperty("hibernate.use_sql_comments", "false");
        hibernateProperties.setProperty("hibernate.format_sql", "true");
        hibernateProperties.setProperty("hibernate.hbm2ddl.auto", "update");
        hibernateProperties.setProperty("hibernate.generate_statistics", "false");
        hibernateProperties.setProperty("javax.persistence.validation.mode", "none");

        //Audit History flags
        hibernateProperties.setProperty("org.hibernate.envers.store_data_at_delete", "true");
        hibernateProperties.setProperty("org.hibernate.envers.global_with_modified_flag", "true");

        return hibernateProperties;
    }

    @Bean
    public PlatformTransactionManager transactionManager() {
        return new JpaTransactionManager();
    }

    @Bean
    public TransactionTemplate transactionTemplate() {
        return new TransactionTemplate(transactionManager());
    }
}

SpringBootプログラムを再度実行し、問題を解決します.