Java Jackson正在返回重复的行

我试图从这两个实体类返回json

Questions.java

@Entity
public class Questions {

@Id
@Column(name = "id")
private  int id;

@Column(name = "question")
private String question;

@Column(name = "type")
private String type;

@Column(name = "description")
private String description;

@Column(name = "param")
private String param;

@Column(name = "maxlength")
private int maxlength;

@Column(name = "dependency")
private String dependency;

@OneToMany(mappedBy = "questions",targetEntity = Answers.class, cascade =    CascadeType.ALL)
private Set<Answers> answers = new HashSet<>();

public int getId() {
    return id;
}

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

public String getQuestion() {
    return question;
}

public void setQuestion(String question) {
    this.question = question;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public String getParam() {
    return param;
}

public void setParam(String param) {
    this.param = param;
}

public int getMaxlength() {
    return maxlength;
}

public void setMaxlength(int maxlength) {
    this.maxlength = maxlength;
}

public String getDependency() {
    return dependency;
}

public Set<Answers> getAnswers() {
    return answers;
}

public void setAnswers(Set<Answers> answers) {
    this.answers = new HashSet<>(answers);
    for(Answers answers1:answers){
        answers1.setQuestions(this);
    }
}

public void setDependency(String dependency) {
    this.dependency = dependency;
}
}

@Entity
public class Answers {

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

@Column(name = "ans_label")
private String ans_label;

@Column(name = "ans_value")
private int ans_value;

@Column(name = "ans_weightage")
private int ans_weightage;

@Column(name = "is_default")
private int is_default;

@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "ques_id", nullable = false)
private Questions questions;

public int getId() {
    return id;
}

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

public String getAns_label() {
    return ans_label;
}

public void setAns_label(String ans_label) {
    this.ans_label = ans_label;
}

public int getAns_value() {
    return ans_value;
}

public void setAns_value(int ans_value) {
    this.ans_value = ans_value;
}

public int getAns_weightage() {
    return ans_weightage;
}

public void setAns_weightage(int ans_weightage) {
    this.ans_weightage = ans_weightage;
}

public int getIs_default() {
    return is_default;
}

public void setIs_default(int is_default) {
    this.is_default = is_default;
}

public Questions getQuestions() {
    return questions;
}

public void setQuestions(Questions questions) {
    this.questions = questions;
}
}

我的控制器看起来像这样

SaveApiController

@RequestMapping("/getData")
public @ResponseBody List<Questions> getData(){
    List<Questions> questionss=saveApiServices.getQuestions();
    return questionss;
}

我的数据库只插入了一行。在我的控制器上只有一个问题列表。但无论何时抛出json输出，它都会重复许多相同的行，如上面的json示例中所示

---

可能有什么问题？如果你找不到完整的解决方案，你能告诉我在json格式中复制相同值的原因吗

杰克逊在这里陷入了困境。您的

问题

类有一个指向

答案

的链接，该类将返回到

问题

解决方案

---

将

问题

字段或

答案

类中的getter标记为

@JsonIgnored

您可以尝试

@JsonManagedReference

和

@JsonBackReference

注释

为了使Jackson能够很好地工作，不应该序列化关系的两个方面之一，以避免导致stackoverflow错误的infite循环

@OneToMany(mappedBy = "questions",targetEntity = Answers.class, cascade =    CascadeType.ALL)
@JsonManagedReference
private Set<Answers> answers = new HashSet<>();

@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "ques_id", nullable = false)
@JsonBackReference
private Questions questions;

@OneToMany（mappedBy=“questions”，targetEntity=Answers.class，cascade=CascadeType.ALL）
@JsonManagedReference
私有集answers=newhashset（）；
@manytone（cascade=CascadeType.ALL，fetch=FetchType.EAGER）
@JoinColumn（name=“ques_id”，nullable=false）
@JsonBackReference
私人问题；

或

---

如果对获取一些实体数据不感兴趣，只需在类中的任何一个中使用

@JsonIgnore

，你怎么能期望有人读取你的非匹配json。。

@OneToMany(mappedBy = "questions",targetEntity = Answers.class, cascade =    CascadeType.ALL)
@JsonManagedReference
private Set<Answers> answers = new HashSet<>();

@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "ques_id", nullable = false)
@JsonBackReference
private Questions questions;