项目中遇到的问题

一、spring boot 中 bean 循环引用

问题复现：三个bean ，都是按构造函数的方式注入，其实现如下

code 01

@Service
@AllArgsConstructor
public class GoodsServiceImpl implements GoodsService {

        private final OrderService orderService;

}

code 02

@Service
@AllArgsConstructor
public class OrderServiceImpl implements OrderService {

    private final UserService userService;

}

code 03

@Service
@AllArgsConstructor
public class UserServiceImpl implements UserService {

    private final GoodsService goodsService;
}

此时，如果启动项目，报错。系统提示出现 bean 的循环引用，导致无法启动

┌─────┐
|  goodsServiceImpl defined in file [D:workstl-shoppingstl-order	argetclassesstlserviceimplGoodsServiceImpl.class]
↑     ↓
|  orderServiceImpl defined in file [D:workstl-shoppingstl-order	argetclassesstlserviceimplOrderServiceImpl.class]
↑     ↓
|  userServiceImpl defined in file [D:workstl-shoppingstl-order	argetclassesstlserviceimplUserServiceImpl.class]
└─────┘

分析：这里都是采用构造参数的方式注入bean 属性，如果使用 @Autowire 系统是否依然报错？

嗯？没有报错，是的，系统正常启动，原因待续

二、项目中浮点计算的陷阱

问题重现：某个实体类统计金额，传入的都是 double 类型的数据，计算总额需要对传入的数据四则运算

 public PaymentWithdrawTotalVO(Double income,Double expend,Double refund,Double deposit) {
        this.subscribeIncome = income == null ? 0d : income;
        this.subscribeExpend = expend == null ? 0d : expend;
        this.subscribeRefund = refund == null ? 0d : refund;
        this.withdrawDeposit = deposit == null ? 0d : deposit;
        this.remainAmount = this.subscribeIncome + this.subscribeRefund - this.withdrawDeposit - this.subscribeExpend;
    }

浮点数参与四则运算出现误差，原因还是由于其存储结构导致的。解决办法:涉及浮点数计算使用 BigDecimal 代替

  public PaymentWithdrawTotalVO(Double income,Double expend,Double refund,Double deposit) {
        this.subscribeIncome = income == null ? 0d : income;
        this.subscribeExpend = expend == null ? 0d : expend;
        this.subscribeRefund = refund == null ? 0d : refund;
        this.withdrawDeposit = deposit == null ? 0d : deposit;
        this.remainAmount = new BigDecimal(subscribeIncome.toString())
                .add(new BigDecimal(subscribeRefund.toString()))
                .subtract(new BigDecimal(withdrawDeposit.toString()))
                .subtract(new BigDecimal(subscribeExpend.toString()))
                .doubleValue();
    }

三、post 请求部分字段居然是null

在一次使用 post 请求的时候，传入2个参数，userId 字段一直是 null

问题排查：请求的过程，传递的参数都正确，尝试改变下字段的名称

换了个字段，传递参数居然是正确的。那么 userId 为何无法传递参数呢？

尝试多种方式传递，发现一个特点：只有userId 不能传递。，仔细看了下代码，原来别人写了参数过滤器 Filter ,我 @#$#@@$$#$@, 经过一场乌龙，也找了问题。

四、Mavne 报错

No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?

添加如下配置

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <!--指定你的jdk地址-->
                    <executable>
                        C:Program FilesJavajdk1.8.0_261injavac.exe
                    </executable>
                </configuration>
            </plugin>
        </plugins>
</build>

maven 打 jar 包报错：没有主属性

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <!--指定你的jdk地址-->
                    <executable>
                        C:Program FilesJavajdk1.8.0_261injavac.exe
                    </executable>
                </configuration>
            </plugin>
        </plugins>
 </build>

五、spring boot 集成 Elasticsearch 报错

解决办法：在启动类上中加上一行代码

  System.setProperty("es.set.netty.runtime.available.processors", "false");

原因不明，参考说是 Redis 与 ES（6.x）冲突导致