玩转Spring Cache --- @Cacheable使用在MyBatis的Mapper接口上（解决Null key returned for cache operation）【享学Spring】（上）

java.lang.IllegalArgumentException: Null key returned for cache operation (maybe you are using named params on classes without debug info?) Builder ...

@Configuration
@MapperScan(basePackages = {"com.fsx.dao"})
@PropertySource(value = "classpath:jdbc.properties", ignoreResourceNotFound = false, encoding = "UTF-8")
public class MyBatisConfig {
    @Value("${datasource.username}")
    private String userName;
    @Value("${datasource.password}")
    private String password;
    @Value("${datasource.url}")
    private String url;
    // 配置数据源
    @Bean
    public DataSource dataSource() {
        MysqlDataSource dataSource = new MysqlDataSource();
        dataSource.setUser(userName);
        dataSource.setPassword(password);
        dataSource.setURL(url);
        return dataSource;
    }
    @Bean
    public SqlSessionFactoryBean sqlSessionFactory() {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource());
        // factoryBean.setMapperLocations(); // 若使用全注解写SQL 此处不用书写Mapper.xml文件所在地
        return factoryBean;
    }
}

// @Repository //备注：这个注解是没有必要的    因为已经被@MapperScan扫进去了  
public interface CacheDemoMapper {
    @Select("select * from user where id = #{id}")
    @Cacheable(cacheNames = "demoCache", key = "#id")
    User getUserById(Integer id);
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {RootConfig.class, CacheConfig.class, MyBatisConfig.class})
public class TestSpringBean {
    @Autowired
    private CacheDemoMapper cacheDemoMapper;
    @Autowired
    private CacheManager cacheManager;
    @Test
    public void test1() {
        cacheDemoMapper.getUserById(1);
        cacheDemoMapper.getUserById(1);
        System.out.println("----------验证缓存是否生效----------");
        Cache cache = cacheManager.getCache("demoCache");
        System.out.println(cache);
        System.out.println(cache.get(1, User.class));
    }
}

java.lang.IllegalArgumentException: Null key returned for cache operation (maybe you are using named params on classes without debug info?) Builder[public final com.fsx.bean.User com.sun.proxy.$Proxy51.getUserById(java.lang.Integer)] caches=[demoCache] | key='#id' | keyGenerator='' | cacheManager='' | cacheResolver='' | condition='' | unless='' | sync='false'
  at org.springframework.cache.interceptor.CacheAspectSupport.generateKey(CacheAspectSupport.java:578)
  ...

public abstract class CacheAspectSupport extends AbstractCacheInvoker implements BeanFactoryAware, InitializingBean, SmartInitializingSingleton {
  ...
  private Object generateKey(CacheOperationContext context, @Nullable Object result) {
    Object key = context.generateKey(result);
    if (key == null) {
      throw new IllegalArgumentException("Null key returned for cache operation (maybe you are " + "using named params on classes without debug info?) " + context.metadata.operation);
    }
    return key;
  }
  ...
}

    @Nullable
    protected Object generateKey(@Nullable Object result) {
      if (StringUtils.hasText(this.metadata.operation.getKey())) {
        EvaluationContext evaluationContext = createEvaluationContext(result);
        return evaluator.key(this.metadata.operation.getKey(), this.metadata.methodKey, evaluationContext);
      }
      return this.metadata.keyGenerator.generate(this.target, this.metadata.method, this.args);
    }

    public static void main(String[] args) throws NoSuchMethodException {
        DefaultParameterNameDiscoverer discoverer = new DefaultParameterNameDiscoverer();
        // 实现类CacheDemoServiceImpl能正常获取到方法入参的变量名
        Method method = CacheDemoServiceImpl.class.getMethod("getFromDB", Integer.class);
        String[] parameterNames = discoverer.getParameterNames(method);
        System.out.println(ArrayUtils.toString(parameterNames)); //{id}
        // 直接从method里拿  永远都是arg0/arg1...哦~~~需要注意
        Arrays.stream(method.getParameters()).forEach(p -> System.out.println(p.getName())); //arg0
        // 接口CacheDemoService不能获取到方法的入参
        method = CacheDemoService.class.getMethod("getFromDB", Integer.class);
        parameterNames = discoverer.getParameterNames(method);
        System.out.println(ArrayUtils.toString(parameterNames)); //{}
        method = CacheDemoMapper.class.getMethod("getUserById", Integer.class);
        parameterNames = discoverer.getParameterNames(method);
        System.out.println(ArrayUtils.toString(parameterNames)); //{}
        //虽然DefaultParameterNameDiscoverer拿不到，但是method自己是可以拿到的，只是参数名是arg0/arg1... 这样排序的
        Arrays.stream(method.getParameters()).forEach(p -> System.out.println(p.getName())); //arg0
    }