龙目岛-java.lang.StackOverflowError:toString方法上为null

问题描述

我有两个类Product和Categorie.如下面的代码所示，当我想用​​categoryRepository.save(c1)修改类别的产品列表时，会发生此错误:

I have two classes Product and Categorie. When I would like to modify the list of products in categorie with categoryRepository.save(c1) as shown in the code below, this error occurs:

 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());
            });

        };
    }

有人可以解决这个问题吗?谢谢.

Can anyone have an idea to solve this issue? Thanks.

推荐答案

您在Lombok生成的toString方法中具有循环引用.

You are having a circular reference in the toString method generated by Lombok.

• Product引用了toString上的Categorie，引用了Product，依此类推

• Product is referencing Categorie on toString, which is referencing Product, and so on

您可以使用排除属性@ToString，但很快就会弃用它，因此请使用@ToString.Exclude:

You could use the exclude a property @ToString, but it is going to be deprecated soon, so use the @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引用此处和此处

Lombok refs here and here

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