问题总结

1. FastJson 泛型转换踩坑，缓存问题 ： http://blog.csdn.net/ykdsg/article/details/50432494

2. Spring中properties配置文件参数读取问题，Spring 父子容器，参见：http://blog.csdn.net/fouy_yun/article/details/48437505      https://www.cnblogs.com/hafiz/p/5875740.html

    AOP扫描也需要注意 父子容器问题，另外，要启用AspectJ对Annotation的支持：<aop:aspectj-autoproxy/>   

3. jar找不到：双击tomcat看配置文件，Server Location中通过 Server path 可以查看eclipse中临时项目位置(tomcat部署的实际项目)

4. tomcat启动项目，一直找不到某些jar：可能是缓存问题，mvn clean package 清除缓存，成功重新打包试试

5. 引入mvn仓库没有的jar包，首先将jar包拷贝到lib目录下，然后pom.xml配置：    

<dependency>
        <groupId>com.tencent.xinge</groupId>
        <artifactId>PushJavaSDK</artifactId>
        <version>1.0</version>
        <scope>system</scope>
        <systemPath>${project.basedir}/lib/PushJavaSDK.jar</systemPath>
  </dependency>

  <!-- 打war包时，将jar包拷贝进去 -->
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-war-plugin</artifactId>
        <configuration>
            <webResources>
                <resource>
                    <directory>${project.basedir}/../erp-service/lib</directory>
                    <targetPath>WEB-INF/lib</targetPath>
                    <filtering>false</filtering>
                    <includes>
                        <include>**/*.jar</include>
                    </includes>
                </resource>
            </webResources>
        </configuration>
        <version>2.1.1</version>
    </plugin>

 6. 分布式锁：     

        String lockKey = LockConstants.LOCK_KEY_ACTIVE_LEAGUE_PREFIX + activateCarUnionDTO.getDealerId();
        if (!redissonLockService.tryLock(lockKey)) {
            return RespMsg.fail("重复请求");
            //直接返回
        }



@Slf4j
@Service("redissonLockService")
public class RedissonLockServiceImpl implements LockService {

    @Autowired
    @Qualifier("redisson")
    private RedissonClient redisson;

    @Override
    public boolean tryLock(String key) {
        return tryLock(key, 0L, TimeUnit.SECONDS);
    }

    @Override
    public boolean tryLock(String key, long timeout, TimeUnit unit) {
       return tryLock(key,timeout, LockService.DEFAULT_EXPIRE_TIME,unit);
    }

    @Override
    public boolean tryLock(String key,long waitTime, long leaseTime, TimeUnit unit) {
        try {
            RLock lock = redisson.getLock(key);
            boolean res = lock.tryLock(waitTime, leaseTime, unit);
            return res;
        } catch (InterruptedException e) {
            RedissonLockServiceImpl.log.error("获取redis锁异常, key is {}, timeout is {},leaseTime is {}, unit is {}.", key, waitTime,leaseTime, unit,
                    e);
            throw new LockException(RespStatusEnum.FAIL,"缓存锁定失败");
        }
    }

    @Override
    public void lock(String key) {
        RLock lock = redisson.getLock(key);
        lock.lock();
    }

    @Override
    public void unLock(String key) {
        RLock lock = redisson.getLock(key);
        lock.unlock();
    }

}

 7. 校验返回值工具类：

public class RespUtils {

    private static Logger logger= LoggerFactory.getLogger(RespUtils.class);

    public  static <T>T resultWithCheck(RespDTO<T> respDTO, String serviceName) throws ServiceException {
        if (respDTO.getStatus() != RespStatusEnum.SUCCESS.getStatus()) {
            logger.error("调用{}服务异常，返回结果，status:{},msg:{}",serviceName, respDTO.getStatus(), respDTO.getMsg());
            throw new ServiceException(respDTO.getMsg());
        }
        return respDTO.getData();
    }


    public  static <T>T resultWithCheck(RespMsg<T> respDTO, String serviceName) throws ServiceException {
        if (respDTO.getStatus() != RespStatusEnum.SUCCESS.getStatus()) {
            logger.error("调用{}服务异常，返回结果，status:{},msg:{}",serviceName, respDTO.getStatus(), respDTO.getMsg());
            throw new ServiceException(respDTO.getMsg());
        }
        return respDTO.getData();
    }

    public  static <T>T resultWithCheck(RespMsg<T> respDTO, String serviceName, String callMethod) throws ServiceException {
        if (respDTO.getStatus() != RespStatusEnum.SUCCESS.getStatus()) {
            logger.error("调用{}服务异常，返回结, callMethod:{}, status:{},msg:{}",serviceName, callMethod, respDTO.getStatus(), respDTO.getMsg());
            throw new ServiceException(respDTO.getMsg());
        }
        return respDTO.getData();
    }
    
    public static <T>T  resultWithCheck(com.mljr.car.league.common.dto.RespDTO<T> respDTO, String serviceName) throws ServiceException {
        if (respDTO.getRc() != RespCodeEnum.SUCCESS.getStatus()) {
            logger.error("调用{}服务异常，返回结果，status:{},msg:{}",serviceName, respDTO.getRc(), respDTO.getMsg());
            throw new ServiceException(respDTO.getMsg());
        }
        return respDTO.getData();
    }
}

 8. 数据库字段设置唯一索引，如果继续插入重复数据，可能导致异常。这种异常需要明确提示“数据重复”。可以通过判断异常名称，来确定返回信息。

catch(Exception e){
            String local = e.getMessage();
            logger.info("local{}"+local);
            String localizeMsg = e.getLocalizedMessage();
            logger.info("localizeMsg{}"+localizeMsg);
            if(localizeMsg.contains("MySQLIntegrityConstraintViolationException")){
                return RespMsg.fail("车商门店重复，无法添加");
            }
            
            logger.error(msg,e);
        }

 9. 泛型     

// 成员变量泛型在 类上声明？  
// 方法参数泛型，在方法上声明？
@Data
public class RespMsg<T,V> {
    private String msg;
    private int status;
    private  T   data;
    private  V   data2;

    public RespMsg(String msg,int status,T data){
         this.msg = msg;
         this.status = status;
         this.data = data;
    }


    public <T,E> void test(T data,E date){
    }
}

10. Stream用法： (https://www.ibm.com/developerworks/cn/java/j-lo-java8streamapi/)：

      List<String> output = wordList.stream().map(String::toUpperCase).collect(Collectors.toList());

11. Spring自动注入properties文件：http://1358440610-qq-com.iteye.com/blog/2090955

12. Java 8:通过反射获取参数名：在Java 8中，使用javac编译器的时候加上-parameters参数的话，会在生成的.class文件中额外存储参数的元信息。当你输入javac -help的时候，你会看到-parameters这个选项

      参见：http://deepinmind.iteye.com/blog/2046050