Springboot整合Hibernate拦截器时无法向拦截器注入Bean

• 开发环境

  JDK 1.8

  Springboot 2.1.1.RELEASE

  pom配置

  <parent>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-parent</artifactId>
          <version>2.1.1.RELEASE</version>
          <relativePath/> <!-- lookup parent from repository -->
      </parent>
  
      <dependencies>
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-data-jpa</artifactId>
          </dependency>
  
          <dependency>
              <groupId>mysql</groupId>
              <artifactId>mysql-connector-java</artifactId>
              <version>8.0.13</version>
          </dependency>
  
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-test</artifactId>
              <scope>test</scope>
          </dependency>
      </dependencies>

  关键代码实体类

  @Entity
  public class User implements Serializable {
  
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Integer id;
  
      private String name;
  
      public Integer getId() {
          return id;
      }
  
      public void setId(Integer id) {
          this.id = id;
      }
  
      public String getName() {
          return name;
      }
  
      public void setName(String name) {
          this.name = name;
      }
  }

  Repository

  public interface UserRepository extends JpaRepository<User,Integer> {
  
  }

  自定义服务

  @Service
  public class MyService {
  
      public void print(){
          System.out.println(this.getClass().getSimpleName()+" call");
      }
  }

  拦截器

  public class SimpleInterceptor extends EmptyInterceptor {
  
      @Resource
      private MyService myService;
  
      @Override
      public String onPrepareStatement(String sql) {
          myService.print();
          System.out.println("sql:"+sql);
          return super.onPrepareStatement(sql);
      }
  }

  启动类

  @SpringBootApplication
  public class BootHibernateInterceptorProblemApplication {
  
      public static void main(String[] args) {
          SpringApplication.run(BootHibernateInterceptorProblemApplication.class, args);
      }
  
  }

  配置

  ## DataSource
  spring.datasource.url=jdbc:mysql://localhost:3306/demo?characterEncoding=utf8&useSSL=true
  spring.datasource.username=root
  spring.datasource.password=123456789
  
  ## hibernate
  spring.jpa.hibernate.ddl-auto=update
  ## add interceptor
  spring.jpa.properties.hibernate.ejb.interceptor=com.rjh.interceptor.SimpleInterceptor

  单元测试类

  @RunWith(SpringRunner.class)
  @SpringBootTest
  public class BootHibernateInterceptorProblemApplicationTests {
  
      @Resource
      private UserRepository userRepository;
  
      @Test
      public void contextLoads() {
          System.out.println(userRepository.findAll());
      }
  
  }

  运行结果

  java.lang.NullPointerException
      at com.rjh.interceptor.SimpleInterceptor.onPrepareStatement(SimpleInterceptor.java:20)
      ...
      ...
      ...

  分析

  根据异常信息，猜测是注入MyService失败

  修改单元测试

  @RunWith(SpringRunner.class)
  @SpringBootTest
  public class BootHibernateInterceptorProblemApplicationTests {
  
      @Resource
      private UserRepository userRepository;
  
      @Resource
      private MyService myService;
  
      @Resource
      private SimpleInterceptor simpleInterceptor;
  
      @Test
      public void contextLoads() {
          Assert.assertNotNull(myService);
          Assert.assertNotNull(simpleInterceptor);
          System.out.println(userRepository.findAll());
      }
  
  }

  运行结果

  Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.rjh.interceptor.SimpleInterceptor' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@javax.annotation.Resource(shareable=true, lookup=, name=, description=, authenticationType=CONTAINER, type=class java.lang.Object, mappedName=)}
      ...

  分析

  根据异常信息可知，Spring的IoC容器中并没有SimpleInterceptor这个Bean，从此处可知spring.jpa.properties.hibernate.ejb.interceptor=com.rjh.interceptor.SimpleInterceptor并没有把这个拦截器注册到Spring容器中

  失败方案

  在SimpleInterceptor上添加@Component注解，将SimpleInterceptor注册到Spring容器中。同时注释spring.jpa.properties.hibernate.ejb.interceptor配置

  失败：SimpleInterceptor的构造方法触发了两次，添加到Hibernate中的SimpleInterceptor实例和注册到Spring容器中的SimpleInterceptor实例并不是同一个实例

  解决方法

  增加一个获取Spring的ApplicationContext实例的工具类，通过这个工具类调用需要注入的服务的方法

  工具类

  @Component
  public class SpringContextUtil implements ApplicationContextAware {
  
      private static ApplicationContext applicationContext;
  
      @Override
      public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
          SpringContextUtil.applicationContext=applicationContext;
      }
  
      public static ApplicationContext getApplicationContext() {
          return applicationContext;
      }
  }

  修改拦截器

  public class SimpleInterceptor extends EmptyInterceptor {
  
      @Override
      public String onPrepareStatement(String sql) {
          MyService myService= SpringContextUtil.getApplicationContext().getBean(MyService.class);
          myService.print();
          System.out.println("sql:"+sql);
          return super.onPrepareStatement(sql);
      }
  
  }

  执行结果

  MyService call
  sql:select user0_.id as id1_0_, user0_.name as name2_0_ from user user0_
  []

  文章来源：segmentfault，作者：Null。