递归 JSON 输入导致 SyntaxError：JSON.parse 处 JSON 输入意外结束答案

【问题标题】：Recursive JSON input causes SyntaxError: Unexpected end of JSON input at JSON.parse递归 JSON 输入导致 SyntaxError：JSON.parse 处 JSON 输入意外结束
【发布时间】：2020-02-06 11:24:38
【问题描述】：

我已经做了好几个小时了，我似乎可以解决这个问题。我有两个实体 Products 和 Customer ，一个客户可以有一个产品，而一个产品可能有很多客户。在我的 SQL SERVER Management Studio 中，Product 表的主键作为 Customer 表中的外键。

我在下面的代码中显示了这两个实体。问题是客户“c”被递归地附加到“myproducts”，这是我在浏览器窗口上检查控制台时显示的 JSON 中的 mappedBy 属性。（请参阅下面错误中的嵌套对象“myproducts”和“c”）

我正在使用 GET 方法 API 在屏幕上显示客户。

Products.java

@Entity
@Table(name="NewProductDetails")
public class Products{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "p_id")
    private int productId;

    @Size(max=65)
    @Column(name = "p_name")
    private String name;

    @Column(name = "p_price")
    private int price;


    @OneToMany(fetch = FetchType.LAZY,
              cascade = CascadeType.ALL,
              mappedBy = "myproduct")
    public  Set<Customer> c;

    public Products() {

    }


    public Products(String p_name, int p_price) {
        this.name = p_name;
        this.price = p_price;
    }

    public long getproductId() {
        return productId;
    }

    public void setproductId(int id) {
        this.productId = id;
    }

    public void setPName(String p_name) {
        this.name = p_name;
    }

    public String getPName() {
        return this.name;
    }

    public void setPrice(int p_price ) {
        this.price  = p_price ;
    }

    public int getPrice() {

        return this.price;
    }

}

ProductController.java

@CrossOrigin(origins = "http://localhost:4200")
@RestController
@RequestMapping("/api")
public class ProductController {

    @Autowired
    ProductRepository productRepository;

    @GetMapping("/product")
    public List<Products> getAllProducts(){
        System.out.println("Get All the product .... ");

        List<Products> products = new ArrayList<>();
        productRepository.findAll().forEach(products :: add);

        return products;
    }

    @GetMapping("/product/{id}")
    public ResponseEntity<Products> findByProductId(@PathVariable("p_id") Long p_id ){
        Optional<Products> prod_ = productRepository.findByProductId(p_id);
        return ResponseEntity.ok(prod_.get());
    }


    @PostMapping(value = "/product")
    public Products postProducts(@RequestBody Products product) {
        Products _product = productRepository.save(new Products(product.getPName(), product.getPrice() ));
        return _product;
    }
}

ProductRepository.java

@Repository
public interface ProductRepository extends CrudRepository<Products, Long>{

    Optional<Products> findByProductId(Long p_id);
}

CustomerRepository.java

@CrossOrigin(origins = "http://localhost:4200")
@RestController
@RequestMapping("/api")
public class CustomerController {

    @Autowired
    CustomerRepository repository;

    @GetMapping("/customer")
    public List<Customer> getAllCustomers() {
        System.out.println("HOOHAAH Get all Customers...");

        List<Customer> customers = new ArrayList<>();
        repository.findAll().forEach(customers::add);
        System.out.println(customers);
        return customers;
    }

    @GetMapping("/customer/{id}")
    public ResponseEntity<Customer> findById(@PathVariable("id") Long Id){
            Optional<Customer> cust_ = repository.findById(Id);
            return ResponseEntity.ok(cust_.get());
    }

    @PostMapping(value = "/customer")
    public Customer postCustomer(@RequestBody Customer customer) {

        Customer _customer = repository.save(new Customer(customer.getName(), customer.getAge(), customer.getProduct()));
        return _customer;
    }

    @DeleteMapping("/customer/{id}")
    public ResponseEntity<String> deleteCustomer(@PathVariable("id") long id) {
        System.out.println("Delete Customer with ID = " + id + "...");

        repository.deleteById(id);

        return new ResponseEntity<>("Customer has been deleted!", HttpStatus.OK);
    }

    @DeleteMapping("/customer")
    public ResponseEntity<String> deleteAllCustomers() {
        System.out.println("Delete All Customers...");

        repository.deleteAll();

        return new ResponseEntity<>("All customers have been deleted!", HttpStatus.OK);
    }

    @GetMapping(value = "customer/age/{age}")
    public List<Customer> findByAge(@PathVariable int age) {

        List<Customer> customers = repository.findByAge(age);
        return customers;
    }


    @PutMapping("/customer/{id}")
    public ResponseEntity<Customer> updateCustomer(@PathVariable("id") long id, @RequestBody Customer customer) {
        System.out.println("Update Customer with ID = " + id + "...");

        Optional<Customer> customerData = repository.findById(id);

        if (customerData.isPresent()) {
            Customer _customer = customerData.get();
            _customer.setName(customer.getName());
            _customer.setAge(customer.getAge());
            _customer.setActive(customer.isActive());
            return new ResponseEntity<>(repository.save(_customer), HttpStatus.OK);
        } else {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
    }
}

主要

@SpringBootApplication
public class SpringRestMySqlApplication implements CommandLineRunner {


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

    @Override
    public void run(String... args) throws Exception {



        //Create Product Instance
        Products prods = new Products();

        //Create Customer instance
        Customer custs = new Customer();


    }

}

浏览器显示错误 SyntaxError: JSON.parse () at XMLHttpRequest.onLoad 的 JSON 输入意外结束

"[{"id":6,"name":"Asma","age":18,"active":true,"myproduct":{"productId":2,"price":4,"c":[{"id":6,"name":"Asma","age":18,"active":true,"myproduct":{"productId":2,"price":4,"c":[{"id":6,.....

服务器日志错误

    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:145) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:107) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:145) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:107) ~[jackson-databind-2.9.6.jar:2.9.6]
    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25) ~[jackson-databind-2.9.6.jar:2.9.6]

........

【问题讨论】：

尝试在你的模型类中添加implements Serializable。 (Products.java)
我这样做了，但没有用。此外，我看不出可序列化对我的情况有何帮助。
你能从服务器日志中发布错误吗？
@EugenCovaci 我已经做到了。请检查编辑后的帖子
你也应该看到这两个帖子..stackoverflow.com/a/18288939/6446770和stackoverflow.com/questions/3325387/…

标签： java json hibernate spring-boot angular8

【解决方案1】：

我在每个实体（产品和客户）中使用 @JsonIgnoreProperties() 解决了错误，并且循环依赖消失了。

我在这个很棒的博客上找到了帮助，通过遵循它的 方法 #3 来解决 JSON 中的递归循环依赖 http://springquay.blogspot.com/2016/01/new-approach-to-solve-json-recursive.html

【讨论】：