spring 配置只读事务_只读副本和Spring Data第3部分：配置两个实体管理器

╰半橙微兮° 2023-02-25 04:00 10阅读 0赞

spring 配置只读事务

我们之前的设置可以正常工作。 我们现在要做的是进一步发展，并配置两个单独的实体管理器，而不会影响我们之前实现的功能。

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第一步是将默认实体管理器配置设置为主要配置。  
这是第一步

package com.gkatzioura.springdatareadreplica.config;  import javax.sql.DataSource;  import org.springframework.beans.factory.annotation.Qualifier;  import org.springframework.beans.factory.annotation.Value;  import org.springframework.boot.jdbc.DataSourceBuilder;  import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;  import org.springframework.context.annotation.Bean;  import org.springframework.context.annotation.ComponentScan;  import org.springframework.context.annotation.Configuration;  import org.springframework.context.annotation.Primary;  import org.springframework.data.jpa.repository.config.EnableJpaRepositories;  import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;  @Configuration  public class PrimaryEntityManagerConfiguration { 
         @Value ( "${spring.datasource.username}" ) 
         private String username; 
         @Value ( "${spring.datasource.password}" ) 
         private String password; 
         @Value ( "${spring.datasource.url}" ) 
         private String url; 
         @Bean 
         @Primary 
         public DataSource dataSource() throws Exception { 
             return DataSourceBuilder.create() 
                                     .url(url) 
                                     .username(username) 
                                     .password(password) 
                                     .driverClassName( "org.postgresql.Driver" ) 
                                     .build(); 
         } 
         @Bean 
         @Primary 
         public LocalContainerEntityManagerFactoryBean entityManagerFactory( 
                 EntityManagerFactoryBuilder builder, 
                 @Qualifier ( "dataSource" ) DataSource dataSource) { 
             return builder.dataSource(dataSource) 
                           .packages( "com.gkatzioura.springdatareadreplica" ) 
                           .persistenceUnit( "main" ) 
                           .build(); 
         }  }

如果您使用此配置运行您的应用程序，它将像之前的应用程序一样运行。  
现在是时候配置只读实体管理器了。

package com.gkatzioura.springdatareadreplica.config;  import javax.sql.DataSource;  import org.springframework.beans.factory.annotation.Qualifier;  import org.springframework.beans.factory.annotation.Value;  import org.springframework.boot.jdbc.DataSourceBuilder;  import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;  import org.springframework.context.annotation.Bean;  import org.springframework.context.annotation.Primary;  import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;  @Configuration  public class ReadOnlyEntityManagerConfiguration { 
         @Value ( "${spring.datasource.username}" ) 
         private String username; 
         @Value ( "${spring.datasource.password}" ) 
         private String password; 
         @Value ( "${spring.datasource.readUrl}" ) 
         private String readUrl; 
         @Bean 
         public DataSource readDataSource() throws Exception { 
             return DataSourceBuilder.create() 
                                     .url(readUrl) 
                                     .username(username) 
                                     .password(password) 
                                     .driverClassName( "org.postgresql.Driver" ) 
                                     .build(); 
         } 
         @Bean 
         public LocalContainerEntityManagerFactoryBean readEntityManagerFactory( 
                 EntityManagerFactoryBuilder builder, 
                 @Qualifier ( "readDataSource" ) DataSource dataSource) { 
             return builder.dataSource(dataSource) 
                           .packages( "com.gkatzioura.springdatareadreplica" ) 
                           .persistenceUnit( "read" ) 
                           .build(); 
         }  }

另外，我将向控制器添加方法以保存模型。

package com.gkatzioura.springdatareadreplica.controller;  import java.util.List;  import org.springframework.http.HttpStatus;  import org.springframework.web.bind.annotation.GetMapping;  import org.springframework.web.bind.annotation.PostMapping;  import org.springframework.web.bind.annotation.RequestBody;  import org.springframework.web.bind.annotation.ResponseStatus;  import org.springframework.web.bind.annotation.RestController;  import com.gkatzioura.springdatareadreplica.entity.Employee;  import com.gkatzioura.springdatareadreplica.repository.EmployeeRepository;  @RestController  public class EmployeeContoller { 
         private final EmployeeRepository employeeRepository; 
         public EmployeeContoller(EmployeeRepository employeeRepository) { 
             this .employeeRepository = employeeRepository; 
         } 
         @GetMapping ( "/employee" ) 
         public List<Employee> getEmployees() { 
             return employeeRepository.findAll(); 
         } 
         @PostMapping ( "/employee" ) 
         @ResponseStatus (HttpStatus.CREATED) @ResponseStatus (HttpStatus.CREATED) 
         public void addEmployee( @RequestBody Employee employee) { 
             employeeRepository.save(employee); 
         }  }

如果您确实尝试使用控制器添加员工，然后查询读取的数据库，您将看到根本没有添加任何条目。

因此，我们已启动并运行了主要的实体管理器，而我们还拥有了辅助的实体管理器。 第二个尚未使用。 下一个[博客][Link 1]着重介绍使用辅助只读实体管理器。

> 翻译自: [https://www.javacodegeeks.com/2019/10/read-replicas-and-spring-data-configuring-two-entity-managers.html][https_www.javacodegeeks.com_2019_10_read-replicas-and-spring-data-configuring-two-entity-managers.html]

spring 配置只读事务

[format_png]: /images/20230209/938149ccfe364e62a3633b019c3c26a3.png
[Link 1]: https://egkatzioura.com/2019/10/10/read-replicas-and-spring-data-part-4-configuring-the-read-repository/
[https_www.javacodegeeks.com_2019_10_read-replicas-and-spring-data-configuring-two-entity-managers.html]: https://www.javacodegeeks.com/2019/10/read-replicas-and-spring-data-configuring-two-entity-managers.html