java - Lombok - java.lang.StackOverflowError : null on toString method

Question

我有两个类 Product 和 Categorie。当我想使用 categoryRepository.save(c1) 修改类别中的产品列表时，如下面的代码所示，出现此错误:

 java.lang.StackOverflowError: null
    at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:449) ~[na:1.8.0_191]
        at java.lang.StringBuilder.append(StringBuilder.java:136) ~[na:1.8.0_191]
        at org.sid.entities.Product.toString(Product.java:12) ~[classes/:na]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_191]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_191]
        at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_191]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_191]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_191]
        at org.sid.entities.Categorie.toString(Categorie.java:15) ~[classes/:na]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_191]

---

@Document
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Categorie {
    @Id
    private String id;
    private String name;
    @DBRef
    @JsonIgnore
    private Collection<Product> products=new ArrayList<>();

@Document
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Product {
    @Id
    private String id;
    private String name;
    private double price;
    @DBRef
    private Categorie categorie;

@Bean
    CommandLineRunner start(CategoryRepository categoryRepository, ProductRepository productRepository){

        return args -> {
            categoryRepository.deleteAll();
            Stream.of("c1 Ordinateur","c2 Imprimente").forEach(c->{
                categoryRepository.save(new Categorie(c.split(" ")[0],c.split(" ")[1],new ArrayList<>()));
            });
            categoryRepository.findAll().forEach(System.out::println);

            productRepository.deleteAll();
            Categorie c1=categoryRepository.findById("c1").get();
            Stream.of("P1","P2","P3","P4").forEach(name->{
               Product p= productRepository.save(new Product(null,name,Math.random()*1000,c1));
               c1.getProducts().add(p);
               categoryRepository.save(c1);
            });

productRepository.findAll().forEach(p->{
                System.out.println(p.toString());
            });

        };
    }

任何人都可以解决这个问题吗？谢谢。

Answer 1

您在 Lombok 生成的 toString 方法中有一个循环引用。

• Product 引用 toString 上的 Categorie，后者引用 Product，依此类推

您可以使用排除属性 @ToString，但它很快就会被弃用，因此请使用 @ToString.Exclude:

@Document
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Product {
  ...

  @ToString.Exclude
  private Categorie categorie;

  ...
}

@Document
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Categorie {
  ...

  @ToString.Exclude
  private Collection<Product> products=new ArrayList<>();

  ...
}

Lombok 引用 here和 here