Springboot整合Hibernate拦截器时无法向拦截器注入Bean

爱被打了一巴掌 2021-12-20 06:11 380阅读 0赞

## 开发环境 ##

1.  `JDK 1.8`
2.  `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/> 
    	</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_
    []