java - Jackson 序列化期间出现异常

Question

我遇到过这个问题，这个问题有点接近 this issue ，但是当我完成所有步骤后，我仍然遇到这样的异常:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: java.util.ArrayList[0]->com.myPackage.SomeEntity["mainEntity"]->com.myPackage.MainEntity["subentity1"]->com.myPackage.Subentity1_$$_javassist_8["handler"])

这是我的实体的代码:

@JsonAutoDetect
public class MainEntity {

    private Subentity1 subentity1;

    private Subentity2 subentity2;

    @JsonProperty
    public Subentity1 getSubentity1() {
        return subentity1;
    }

    public void setSubentity1(Subentity1 subentity1) {
        this.subentity1 = subentity1;
    }

    @JsonProperty
    public Subentity2 getSubentity2() {
        return subentity2;
    }

    public void setSubentity2(Subentity2 subentity2) {
        this.subentity2 = subentity2;
    }
}



@Entity
@Table(name = "subentity1")
@JsonAutoDetect
public class Subentity1 {

    @Id
    @Column(name = "subentity1_id")
    @GeneratedValue
    private Long id;

    @Column(name = "name", length = 100)
    private String name;

    @JsonIgnore
    @OneToMany(mappedBy = "subentity1")
    private List<Subentity2> subentities2;

     @JsonProperty
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @JsonProperty
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    //here I didin't add @JsonProperty, cause it leads to cycling during serialization
    public List<Subentity2> getSubentity2s() {
        return subentity2s;
    }

    public void setSubentity2s(List<Subentity2> subentity2s) {
        this.subentity2s = subentity2s;
    }

}

@Entity
@Table(name = "subentity2")
@JsonAutoDetect
public class Subentity2 {
    @Id
    @Column(name = "subentity2_id")
    @GeneratedValue
    private Long id;

    @Column(name = "name", length = 50)
    private String name;

    @ManyToOne
    @JoinColumn(name = "subentity1_id")
    private Subentity1 subentity1;

    @JsonProperty
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @JsonProperty
    public String getName() {
        return name;
    }

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

    @JsonProperty
    public Subentity1 getSubentity1() {
        return subentity1;
    }

    public void setSubentity1(Subentity1 subentity1) {
        this.subentity1 = subentity1;
    }

这是我的转换方法的代码:

 private String toJSON(Object model) {
        ObjectMapper mapper = new ObjectMapper();
        String result = "";
        try {
            result = mapper.writeValueAsString(model);
        } catch (JsonGenerationException e) {
            LOG.error(e.getMessage(), e);
        } catch (JsonMappingException e) {
            LOG.error(e.getMessage(), e);
        } catch (IOException e) {
            LOG.error(e.getMessage(), e);
        }
        return result;
    }

我将非常感谢任何帮助、建议或代码:)

更新

alsp，我忘记从我的 Controller 添加一段代码:

String result = "";
        List<SomeEntity> entities = someEntityService.getAll();
        Hibernate.initialize(entities);
        for (SomeEntity someEntity : entities) {
            Hibernate.initialize(someEntity.mainEntity());
            Hibernate.initialize(someEntity.mainEntity().subentity1());
            Hibernate.initialize(someEntity.mainEntity().subentity2());
        }
        result = this.toJSON(entities);

我不能忽略任何字段，因为我需要它们

Answer 1

基本上，您的一些字段被包装到惰性 hibernate 代理中。在序列化对象之前调用 Hibernate.initialize(model) ，它将加载您的惰性集合和引用。

但我不会混合数据库和 View 模型，这是一个不好的做法。为您的 Restful 模型创建一组类，并在序列化之前将数据库实体转换为它们。