确保在任何地方都使用com.fasterxml.jackson。我花了很多时间才弄清楚。

<properties>
  <fasterxml.jackson.version>2.9.2</fasterxml.jackson.version>
</properties>

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>${fasterxml.jackson.version}</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>${fasterxml.jackson.version}</version>
</dependency>

然后使用@JsonManagedReference和@JsonBackReference。

最后，你可以将你的模型序列化为JSON:

import com.fasterxml.jackson.databind.ObjectMapper;

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(model);

在我的情况下，这足以改变关系:

@OneToMany(mappedBy = "county")
private List<Town> towns;

to:

@OneToMany
private List<Town> towns;

另一种关系保持不变:

@ManyToOne
@JoinColumn(name = "county_id")
private County county;

我也遇到了同样的问题。我使用@JsonIdentityInfo的ObjectIdGenerators.PropertyGenerator.class生成器类型。

这就是我的解决方案:

@Entity
@Table(name = "ta_trainee", uniqueConstraints = {@UniqueConstraint(columnNames = {"id"})})
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
public class Trainee extends BusinessObject {
...

在做了更多的分析后，我也有同样的问题，我知道，我们也可以通过在OneToMany注释中保持@JsonBackReference来获得映射实体

@Entity
@Table(name = "ta_trainee", uniqueConstraints = {@UniqueConstraint(columnNames = {"id"})})
public class Trainee extends BusinessObject {

@Id
@GeneratedValue(strategy = GenerationType.TABLE)
@Column(name = "id", nullable = false)
private Integer id;

@Column(name = "name", nullable = true)
private String name;

@Column(name = "surname", nullable = true)
private String surname;

@OneToMany(mappedBy = "trainee", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@Column(nullable = true)
@JsonBackReference
private Set<BodyStat> bodyStats;

@JsonIgnoreProperties是答案。

使用如下代码::

@OneToMany(mappedBy = "course",fetch=FetchType.EAGER)
@JsonIgnoreProperties("course")
private Set<Student> students;

对我来说，最好的解决方案是使用@JsonView，并为每个场景创建特定的过滤器。你也可以使用@JsonManagedReference和@JsonBackReference，但是这是一种硬编码的解决方案，只针对一种情况，即所有者总是引用拥有方，而不是相反。如果您有另一个序列化场景，需要以不同的方式重新注释属性，则不能这样做。

问题

让我们使用两个类，Company和Employee，它们之间有循环依赖关系:

public class Company {

    private Employee employee;

    public Company(Employee employee) {
        this.employee = employee;
    }

    public Employee getEmployee() {
        return employee;
    }
}

public class Employee {

    private Company company;

    public Company getCompany() {
        return company;
    }

    public void setCompany(Company company) {
        this.company = company;
    }
}

以及尝试使用ObjectMapper (Spring Boot)序列化的测试类:

@SpringBootTest
@RunWith(SpringRunner.class)
@Transactional
public class CompanyTest {

    @Autowired
    public ObjectMapper mapper;

    @Test
    public void shouldSaveCompany() throws JsonProcessingException {
        Employee employee = new Employee();
        Company company = new Company(employee);
        employee.setCompany(company);

        String jsonCompany = mapper.writeValueAsString(company);
        System.out.println(jsonCompany);
        assertTrue(true);
    }
}

如果你运行这段代码，你会得到:

org.codehaus.jackson.map.JsonMappingException: Infinite recursion (StackOverflowError)

使用“@JsonView”的解决方案

@JsonView允许您在序列化对象时使用过滤器并选择应该包括哪些字段。筛选器只是用作标识符的类引用。让我们先创建过滤器:

public class Filter {

    public static interface EmployeeData {};

    public static interface CompanyData extends EmployeeData {};

} 

请记住，过滤器是虚拟类，仅用于使用@JsonView注释指定字段，因此您可以根据需要创建任意数量的字段。让我们来看看它的实际操作，但首先我们需要注释我们的Company类:

public class Company {

    @JsonView(Filter.CompanyData.class)
    private Employee employee;

    public Company(Employee employee) {
        this.employee = employee;
    }

    public Employee getEmployee() {
        return employee;
    }
}

并更改Test以便序列化器使用视图:

@SpringBootTest
@RunWith(SpringRunner.class)
@Transactional
public class CompanyTest {

    @Autowired
    public ObjectMapper mapper;

    @Test
    public void shouldSaveCompany() throws JsonProcessingException {
        Employee employee = new Employee();
        Company company = new Company(employee);
        employee.setCompany(company);

        ObjectWriter writter = mapper.writerWithView(Filter.CompanyData.class);
        String jsonCompany = writter.writeValueAsString(company);

        System.out.println(jsonCompany);
        assertTrue(true);
    }
}

现在，如果运行这段代码，无限递归问题就解决了，因为您已经显式地说过，您只想序列化用@JsonView(Filter.CompanyData.class)注释的属性。

当它到达Employee中company的后向引用时，它检查它是否没有注释并忽略序列化。您还有一个强大而灵活的解决方案来选择希望通过REST api发送哪些数据。

使用Spring，您可以使用所需的@JsonView过滤器注释REST Controllers方法，序列化将透明地应用到返回的对象。

下面是用于检查的导入:

import static org.junit.Assert.assertTrue;

import javax.transaction.Transactional;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;

import com.fasterxml.jackson.annotation.JsonView;