我正在尝试使用GSON将一个Java对象（以列表格式）转换为JSON。我已经尝试了几种方法，但是都遇到了相同的错误。
第一次尝试
List<Techinv> techs = UserUtil.getTechModels(group, org);
Gson gson = new Gson();
String json = gson.toJson(techs);
第二次尝试
List<Techinv> techs = UserUtil.getTechModels(group, org);
Type listType = new TypeToken<List<Techinv>>() {}.getType();
Gson gson = new Gson();
String json = gson.toJson(techs, listType);
第三次尝试
List<Techinv> techs = UserUtil.getTechModels(group, org);
GsonBuilder gsonBuilder = new GsonBuilder();
new GraphAdapterBuilder()
.addType(Techinv.class)
.registerOn(gsonBuilder);
Gson gson = gsonBuilder.create();
String json = gson.toJson(techs);
所有上述方法都失败了，要么是出现了
stackoverflow错误，要么是将我的Techinv类中的一个成员变量（java int类型）转换为java向量时出错，这些问题都出现在GSON库中。请告诉我在所有这些示例中我是否遗漏了一些简单的东西 :)
Techinv类（如果需要）：
package org.cchit.inv.model;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.Lob;
import javax.persistence.ManyToOne;
import javax.persistence.NamedNativeQueries;
import javax.persistence.NamedNativeQuery;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
/**
* The persistent class for the techinv database table.
*
*/
@Entity
@NamedNativeQueries ({
@NamedNativeQuery(name="Techinv.deleteByOrgId",
query="DELETE FROM techinv where org_id = ?")
})
@NamedQueries ({
@NamedQuery(name="Techinv.removeUser",
query="UPDATE Techinv t SET user_id = 0 where t.id = :techid"),
@NamedQuery(name="Techinv.getAllByOrg",
query="SELECT p FROM Techinv p where p.organization.liferayId = :orgid"),
@NamedQuery(name="Techinv.getById",
query="SELECT t FROM Techinv t where t.id = :id"),
@NamedQuery(name="Techinv.getByProdOrg",
query="SELECT p FROM Techinv p where p.organization.liferayId = :orgid and p.product.id = :prodid"),
@NamedQuery(name="Techinv.delete",
query="DELETE FROM Techinv t where t.id = :id")
})
@Table(name="techinv")
public class Techinv implements Serializable {
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
@Column(name="mu_mask")
private long muMask;
@Column(name="mu_assigned_mask")
private long muAssignedMask;
@Column(name="mu_asked_assign_mask")
private long muAskedAssignedMask;
@Column(name="mu_cert_mask")
private long muWillCertMask;
@Column(name="mu_ask_will_cert_mask")
private long muAskedWillCertMask;
@Column(name="certType")
private String certType;
@Temporal(TemporalType.DATE)
@Column(name="Apply_date")
private Date applyDate;
@Temporal(TemporalType.DATE)
@Column(name="Cert_date")
private Date certDate;
@Lob()
private String notes;
//bi-directional many-to-one association to OrgUser
@ManyToOne
@JoinColumn(name="user_id")
private OrgUser orgUser;
//bi-directional many-to-one association to Organization
@ManyToOne
@JoinColumn(name="org_id")
private Organization organization;
//bi-directional many-to-one association to Product
@ManyToOne
@JoinColumn(name="prod_id")
private Product product;
//bi-directional many-to-one association to Certification
@ManyToOne
@JoinColumn(name="cert_id")
private Certification certification;
public void setCertification(Certification certification) {
this.certification = certification;
}
public Product getProduct() {
return product;
}
public void setProduct(Product product) {
this.product = product;
}
public Techinv() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public String getNotes() {
return this.notes;
}
public void setNotes(String notes) {
this.notes = notes;
}
public OrgUser getOrgUser() {
return this.orgUser;
}
public void setOrgUser(OrgUser orgUser) {
this.orgUser = orgUser;
}
public Organization getOrganization() {
return this.organization;
}
public void setOrganization(Organization organization) {
this.organization = organization;
}
public long getMuMask() {
return muMask;
}
public void setMuMask(long muMask) {
this.muMask = muMask;
}
public long getMuAssignedMask() {
return muAssignedMask;
}
public void setMuAssignedMask(long muAssigned) {
this.muAssignedMask = muAssigned;
}
public Certification getCertification() {
return certification;
}
public long getMuWillCertMask() {
return muWillCertMask;
}
public void setMuWillCertMask(long muWillCertMask) {
this.muWillCertMask = muWillCertMask;
}
public long getMuAskWillCertMask() {
return muAskedWillCertMask;
}
public void setMuAskedWillCertMask(long muAskedWillCertMask) {
this.muAskedWillCertMask = muAskedWillCertMask;
}
/**
* This will set the question to true. Once asked and answered, this cannot be unset.
* @param mu
*/
public void setMuAskedAssignedMask(Mu mu) {
this.muAskedAssignedMask |= mu.getMask();
}
public boolean isCertified(Mu mu) {
return getCertification() != null && (getCertification().getMuMask() & mu.getMask()) > 0;
}
public boolean isAssigned(Mu mu) {
return (getMuAssignedMask() & mu.getMask()) > 0;
}
public boolean hasAskedToCertify(Mu mu) {
return isAssigned(mu) && !isCertified(mu) && (getMuAskWillCertMask() & mu.getMask()) > 0;
}
public boolean isWillCertify(Mu mu) {
return hasAskedToCertify(mu) && (getMuWillCertMask() & mu.getMask()) > 0;
}
public boolean hasMu(Mu mu) {
return (getMuMask() & mu.getMask()) > 0;
}
public boolean hasAskedToAssign(Mu mu) {
return (muAskedAssignedMask & mu.getMask()) > 0;
}
public String getCertType() {
return certType;
}
public void setCertType(String certType) {
this.certType = certType;
}
public Date getApplyDate() {
return applyDate;
}
public void setApplyDate(Date applyDate) {
this.applyDate = applyDate;
}
public Date getCertDate() {
return certDate;
}
public void setCertDate(Date certDate) {
this.certDate = certDate;
}
}