序列化期间的Jackson异常

Question

我已经遇到了这个问题 ， 这个问题与这个问题有点接近，但是当我完成所有步骤后，我仍然有一个例外：

org.codehaus.jackson.map.JsonMappingException：未找到类org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer的序列化器，也未发现创建BeanSerializer的属性（为避免异常，请禁用SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS））（通过引用链） ：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;
    }

我将非常感谢您的帮助，建议或代码:)

UPD

另外，我忘记从控制器中添加一段代码：

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，您的某些字段被包装到懒惰的休眠代理中。 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。

但是我不会混合使用数据库和视图模型，这是一个不好的做法。 为您的静态模型创建一组类，并在序列化之前将数据库实体转换为它们。

Answer 2

我用类中的平面字段（String，Boolean，Double等）创建了一个Bean，并设置了转换方法

Answer 3

如果您使用的是延迟加载，请添加此内容

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})