原因：java.lang.UnsupportedOperationException：空Lombok（带列表）

Question

我正在研究Spring Data JPA + Postgres lombok示例。 在此示例中，我得到以下错误。

java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:782) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:763) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:318) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.example.StockApplication.main(StockApplication.java:18) [classes/:na]
Caused by: java.lang.UnsupportedOperationException: null
    at java.util.AbstractCollection.add(AbstractCollection.java:262) ~[na:1.8.0_171]
    at org.hibernate.collection.internal.PersistentSet.add(PersistentSet.java:211) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final]
    at org.example.StockApplication.run(StockApplication.java:40) [classes/:na]
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:779) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    ... 5 common frames omitted

股票.java

@Builder
@Getter
@AllArgsConstructor
@Entity
@Table(name = "stock", catalog = "mkyongdb", uniqueConstraints = { @UniqueConstraint(columnNames = "STOCK_NAME"),
        @UniqueConstraint(columnNames = "STOCK_CODE") })
public class Stock implements java.io.Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "STOCK_ID", unique = true, nullable = false)
    private Integer stockId;

    @Column(name = "STOCK_CODE", unique = true, nullable = false, length = 10)
    private String stockCode;

    @Column(name = "STOCK_NAME", unique = true, nullable = false, length = 20)
    private String stockName;


    @Singular
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "stock")
    private final Set<StockDailyRecord> stockDailyRecords;
}

StockDailyRecord.java

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "stock_daily_record", catalog = "mkyongdb", uniqueConstraints = @UniqueConstraint(columnNames = "DATE"))
public class StockDailyRecord implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "RECORD_ID", unique = true, nullable = false)
    private Integer recordId;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "STOCK_ID", nullable = false)
    private Stock stock;

    @Column(name = "PRICE_OPEN", precision = 6)
    private Float priceOpen;

    @Column(name = "PRICE_CLOSE", precision = 6)
    private Float priceClose;

    @Column(name = "PRICE_CHANGE", precision = 6)
    private Float priceChange;

    @Column(name = "VOLUME")
    private Long volume;

    @Temporal(TemporalType.DATE)
    @Column(name = "DATE", unique = true, nullable = false, length = 10)
    private Date date;
}

主应用

@SpringBootApplication
public class StockApplication implements CommandLineRunner{

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

    @Autowired
    private StockRepository stockRepository;
    @Autowired
    private StockDailyRecordRepository stockDailyRecordRepository;

    @Override
    public void run(String... args) throws Exception {
        Stock stock = Stock.builder().stockCode("7052").stockName("PADINI").build();
        stockRepository.save(stock);

        StockDailyRecord stockDailyRecords = StockDailyRecord.builder()
                .priceOpen(new Float("1.2"))
                .priceChange(new Float("10.0"))
                .priceClose(new Float("1.1"))
                .date(new Date())
                .volume(3000000L)
                .build();

        stockDailyRecords.setStock(stock);        
        stock.getStockDailyRecords().add(stockDailyRecords); //Line-22
        stockDailyRecordRepository.save(stockDailyRecords);
    }
}

注意：代码在第22行中断

Answer 1

第22行的stockDailyRecords设置可以为null。 在添加值之前进行检查。

if(Objects.nonNull(stock.getStockDailyRecords())){
    stock.getStockDailyRecords().add(stockDailyRecords);
} else {
    Set setA = new HashSet();
    set.add(stockDailyRecords);
    stock.setStockDailyRecords(setA);
}

Answer 2

阅读https://projectlombok.org/features/Builder上的@Singular部分，您应该得到答案。

基本上，在调用build（）之后 ，基础集合将是不可变的，因此不允许添加更多数据。 正确的方法是重用构建器，添加新的stockDailRecords并创建一个新的对象。

不幸的是，由于数据库希望修改同一对象，因此可能会破坏持久性部分。 IMO将此类不可变对象用于此任务根本不明智。

在Lombok Builder注释中引发UnsupportedOperationException时，也已经讨论了一个非常类似的问题