一举庶、Spring使用過程中的踩坑記錄

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• Spring通過注解使用多數(shù)據(jù)源

坑：@Autowired 按 byType 自動(dòng)注入，而 @Resource 則默認(rèn)按 byName 自動(dòng)注入觅玻，@Primary是優(yōu)先選擇疮方。

例如悍募，在項(xiàng)目中是有兩個(gè)Redis源，這兩個(gè)Redis Bean分別為dataRedisTemplate和redisTemplate常侦。

Redis Bean1：dataRedisTemplate浇冰，clusterNodes為${data-redis.cluster.nodes}

@Bean(name = "dataRedisTemplate")
public RedisTemplate dataRedisTemplate() {
    RedisTemplate template = new RedisTemplate();
    template.setConnectionFactory(sessionLettuceConnectionFactory);
    Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
    ObjectMapper om = new ObjectMapper();
    om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
    om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
    jackson2JsonRedisSerializer.setObjectMapper(om);
    template.setKeySerializer(new StringRedisSerializer());
    template.setValueSerializer(jackson2JsonRedisSerializer);
    template.setHashKeySerializer(jackson2JsonRedisSerializer);
    template.setHashValueSerializer(new StringRedisSerializer());
    template.afterPropertiesSet();
    return template;
}

// factory
@Resource
@Qualifier(value = "dataLettuceConnectionFactory")
private RedisConnectionFactory dataLettuceConnectionFactory;

// clusterNodes
@Value("${spring.data-redis.cluster.nodes}")
private String clusterNodes;

Redis Bean2：redisTemplate予弧，clusterNodes為${redis.cluster.nodes}

@Primary
@Bean(name = "redisTemplate")
public RedisTemplate<String, Object> redisTemplate() {
    RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
    redisTemplate.setConnectionFactory(lettuceConnectionFactory);
    redisTemplate.setKeySerializer(new StringRedisSerializer());
    Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
    objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
    jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
    redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
    redisTemplate.setHashKeySerializer(new StringRedisSerializer());
    redisTemplate.setHashValueSerializer(new StringRedisSerializer());
    redisTemplate.afterPropertiesSet();
    return redisTemplate;
}

// factory
@Resource
@Qualifier(value = "lettuceConnectionFactory")
private RedisConnectionFactory lettuceConnectionFactory;

// clusterNodes
@Value("${spring.redis.cluster.nodes}")
private String clusterNodes;

在一個(gè)應(yīng)用中要把數(shù)據(jù)放入到“Redis Bean1：dataRedisTemplate”對(duì)應(yīng)的Redis中，于是我在這個(gè)應(yīng)用中使用方式如下：

@Autowired
private RedisTemplate dataRedisTemplate;

// 根據(jù)key獲取數(shù)據(jù)
Object obj = dataRedisTemplate.opsForValue().get(key);

實(shí)際上使用的是“Redis Bean2：redisTemplate”對(duì)應(yīng)的Redis湖饱。
破解方式一：把@Autowired換成@Resource 注解掖蛤。如下：

@Autowired
private RedisTemplate dataRedisTemplate;

// 把@Autowired換成@Resource

@Resource
private RedisTemplate dataRedisTemplate;

@Autowired和@Resource最大的區(qū)別就是：@Autowired 按 byType 自動(dòng)注入，而 @Resource 則默認(rèn)按 byName 自動(dòng)注入井厌。

這里還需要注意一個(gè)注解@Primary蚓庭，官方的說明如下：

Indicates that a bean should be given preference when multiple candidates are qualified to autowire a single-valued dependency. If exactly one 'primary' bean exists among the candidates, it will be the autowired value.

@Primary 優(yōu)先方案，被注解的實(shí)現(xiàn)仅仆，優(yōu)先被注入

通常情況下@Autowired是通過byType的方法注入的器赞，可是在多個(gè)實(shí)現(xiàn)類的時(shí)候，byType的方式不再是唯一墓拜，而需要通過byName的方式來注入港柜，而這個(gè)name默認(rèn)就是根據(jù)變量名來的。

也就是說咳榜，如果沒有在redisTemplate()上面增加@Primary的話是沒有問題的夏醉，因?yàn)橛卸鄠€(gè)實(shí)現(xiàn)時(shí)，@Autowired是會(huì)通過byName的方式來注入的涌韩，但是按照上面說的畔柔，因?yàn)橛辛薂Primary，@Autowired注解會(huì)優(yōu)先使用Bean redisTemplate臣樱。

還有一種解決方案是增加@Qualifier(value = "dataRedisTemplate")靶擦，如下：

@Autowired
private RedisTemplate dataRedisTemplate;

// 換成：增加@Qualifier(value = "dataRedisTemplate")

@Autowired
@Qualifier(value = "dataRedisTemplate")
private RedisTemplate dataRedisTemplate;

• Spring事務(wù)@Transactional失效問題

坑：若同一類中的其他沒有@Transactional 注解的方法內(nèi)部調(diào)用有@Transactional 注解的方法，有@Transactional 注解的方法的事務(wù)被忽略雇毫，不會(huì)發(fā)生回滾玄捕。

FooService.class

public interface FooService {
    void insertRecord();
    void insertThenRollback() throws Exception;
    void invokeInsertThenRollback() throws Exception;
    void invokeInsertThenRollbackTwo() throws Exception;
}

FooServiceImpl.class

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
import org.springframework.transaction.annotation.Transactional;

@Component
public class FooServiceImpl implements FooService {
    @Autowired
    private JdbcTemplate jdbcTemplate;
    @Autowired
    private FooService fooService;

    @Override
    @Transactional
    public void insertRecord() {
        jdbcTemplate.execute("INSERT INTO FOO (BAR) VALUES ('AAA')");
    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public void insertThenRollback() throws Exception {
        jdbcTemplate.execute("INSERT INTO FOO (BAR) VALUES ('BBB')");
        throw new Exception();
    }

    @Override
    public void invokeInsertThenRollback() throws Exception {
        insertThenRollback();
    }

    @Override
    public void invokeInsertThenRollbackTwo() throws Exception {
        fooService.insertThenRollback();
    }
}

執(zhí)行

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.AdviceMode;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@SpringBootApplication
@EnableTransactionManagement(mode = AdviceMode.PROXY)
@Slf4j
public class DeclarativeTransactionDemoApplication implements CommandLineRunner {
    @Autowired
    private FooService fooService;
    @Autowired
    private JdbcTemplate jdbcTemplate;

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

    @Override
    public void run(String... args) throws Exception {
        // 標(biāo)記1:輸出 AAA 1
        fooService.insertRecord();
        log.info("AAA {}",jdbcTemplate.queryForObject("SELECT COUNT(*) FROM FOO WHERE BAR='AAA'", Long.class));
        
        // 標(biāo)記2:輸出 BBB 0，事務(wù)生效        
        try {
            fooService.insertThenRollback();
        } catch (Exception e) {
            log.info("BBB {}",jdbcTemplate.queryForObject("SELECT COUNT(*) FROM FOO WHERE BAR='BBB'", Long.class));
        }

        // 標(biāo)記3:輸出 BBB 1棚放，事務(wù)未生效
        // ***這個(gè)地方就是最容易踩坑的地方Ｃ墩场！席吴！***        
        try {
            fooService.invokeInsertThenRollback();
        } catch (Exception e) {
            log.info("BBB {}",jdbcTemplate.queryForObject("SELECT COUNT(*) FROM FOO WHERE BAR='BBB'", Long.class));
        }

        // 標(biāo)記4:輸出 BBB 1赌结，事務(wù)生效（如果把標(biāo)記3的代碼注釋掉，輸出 BBB 0）
        // ***這是避免踩坑的一種方式***        
        try {
            fooService.invokeInsertThenRollbackTwo();
        } catch (Exception e) {
            log.info("BBB {}",jdbcTemplate.queryForObject("SELECT COUNT(*) FROM FOO WHERE BAR='BBB'", Long.class));
        }
    }
}

二孝冒、RocketMQ使用過程中的踩坑記錄

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• Rocket默認(rèn)開啟了VIP通道導(dǎo)致10909failed問題
  坑：Rocket默認(rèn)開啟了VIP通道柬姚，VIP通道端口為10911-2=10909。若Rocket服務(wù)器未啟動(dòng)端口10909庄涡，則報(bào)connect to <：10909> failed量承。

解決方案：不走VIP通道。

producer.setVipChannelEnabled(false);
consumer.setVipChannelEnabled(false);

• Rocket instanceName參數(shù)未做配置導(dǎo)致重復(fù)消費(fèi)問題

坑：一個(gè)是Rocket如果沒有配置instanceName，那么會(huì)使用pid做instanceName撕捍，如果instanceName一樣會(huì)重復(fù)消費(fèi)拿穴，因?yàn)榧合M(fèi)模式是按instanceName做為唯一消費(fèi)實(shí)例。

查看源碼忧风，如果沒有指定instanceName默認(rèn)會(huì)把pid做為instanceName默色，如下：

if (this.instanceName.equals("DEFAULT")) {
    this.instanceName = String.valueOf(UtilAll.getPid());
}

public static int getPid() {
    RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();
    String name = runtime.getName(); // format: "pid@hostname"
    try {
        return Integer.parseInt(name.substring(0, name.indexOf('@')));
    }
    catch (Exception e) {
        return -1;
    }
}

解決方案：運(yùn)維配置有$MQ_INSTANCE_NAME 環(huán)境變量，不同機(jī)器不一樣狮腿，所以可以使用：mq.consumer.instanceName:${MQ_INSTANCE_NAME:默認(rèn)值}進(jìn)行配置腿宰。

@Value("${rocketmq.consumer.instanceName:${MQ_INSTANCE_NAME:fota}}")
private String clientInstanceName;

consumer.setInstanceName(clientInstanceName);