检索用户列表时出现StackOverflowError

Question

我试图获取使用bootstrap数据表的用户列表，但我一直得到StackOverflowError。以下是我的代码。

控制器：

@RequestMapping(value = "/admin/login_management", method = RequestMethod.GET)
public ModelAndView loginMgt(HttpServletRequest request, ModelMap m) {
    m.put("login_management", true);
    return new ModelAndView("login_management");
}

（数据表对象）

@RequestMapping(value = "/admin/usersList", method = RequestMethod.GET, produces = "application/json")
public @ResponseBody Object userListPaginationDataTables(@RequestParam(value = "sEcho", required = false) String sEcho,
                                                            @RequestParam(value = "sSearch", required = false) String sSearch,
                                                            @RequestParam(value = "sColumns", required = false) String sColumns,
                                                            @RequestParam(value = "iDisplayStart", required = false) Integer iDisplayStart,
                                                            @RequestParam(value = "iDisplayLength", required = false) Integer iDisplayLength,
                                                            @RequestParam(value = "iColumns", required = false) Integer iColumns,
                                                            @RequestParam(value = "iSortCol_0", required = false) Integer iSortCol_0,
                                                            @RequestParam(value = "iSortColumnIndex", required = false) Integer iSortColumnIndex,
                                                            @RequestParam(value = "sSortDir_0", required = false) String sSortDir_0)
                                                                    throws IOException {
        String json = "";

        List<User> result = new ArrayList<>();

        result = userService.getUserList(iDisplayStart, iDisplayLength);

        int total = userService.getUserTotalSize();

        json = getJSonString(result, total);


    return json;
}

private static String getJSonString(List<?> result, int total){

    String json="";

    try {
        DataTablesObject dataTablesObject = new DataTablesObject();
        dataTablesObject.setAaData(result);
        if(total > 0) {
            dataTablesObject.setiTotalRecords(total);
            dataTablesObject.setiTotalDisplayRecords(total);
        }

        Gson gson = new GsonBuilder().setPrettyPrinting().create();

        json = gson.toJson(dataTablesObject);

    } catch (Exception ex) {

        LOGGER.fatal(ex);
    }

    return json;
}

login_management.jsp：

<script>
    $(function() {          
        $("#example2").dataTable({
            "bServerSide": true,
            "sAjaxSource": "${pageContext.request.contextPath}/admin/usersList",
            "bProcessing": true,
            "bFilter":false,
            "sPaginationType": "bootstrap",
            "bJQueryUI": true,                  
            "aoColumns": [
                { "mData": "id" },
                { "mData": "login" },
                {
                    "mData": null,
                    "mRender": function (data, type, full) {
                        //alert(data);
                        return "<form method='post' action='${pageContext.request.contextPath}/admin/editUser?id=1'>"+
                                    "<button type='submit'class='btn btn-primary'>Edit</button>"+
                                "</form>";

                    },
                    "fnCreatedCell": function ( cell ) {
                        $('input, label', cell)
                            .button( {
                                text: true
                            } );

                    }
                }

            ]
        });
    });
    </script>

型号：

@Entity
@Table(name="user")
public class User {

@Id
@GeneratedValue
private Integer id;

private String login;

private String password;


@OneToOne(cascade=CascadeType.ALL, fetch =FetchType.EAGER)
@JoinTable(name="user_roles",
    joinColumns = {@JoinColumn(name="user_id", referencedColumnName="id")},
    inverseJoinColumns = {@JoinColumn(name="role_id", referencedColumnName="id")}
)
private Role role;

//...getters & setters...
}

角色：

@Entity
@Table(name="roles")
public class Role {

@Id
@GeneratedValue
private Integer id;

private String role;

@OneToMany(cascade=CascadeType.ALL, fetch =FetchType.EAGER)
@JoinTable(name="user_roles", 
    joinColumns = {@JoinColumn(name="role_id", referencedColumnName="id")},
    inverseJoinColumns = {@JoinColumn(name="user_id", referencedColumnName="id")}
)
private Set<User> userRoles;
//...getters and setters...
}

@Entity
@Table(name="user_roles")
public class UserRole {

@Id
@Column(name="user_id")
private Integer id;

@Column(name="role_id")
private Integer roleId;
//...getters and setters...
}

然而，在我编译并启动我的tomcat之后，我收到了这个错误：

SEVERE: Servlet.service() for servlet [dispatcher] in context with path  threw exception     [Handler processing failed; nested exception is java.lang.StackOverflowError] with root cause
java.lang.StackOverflowError
at com.google.gson.stream.JsonWriter.beforeName(JsonWriter.java:580)
at com.google.gson.stream.JsonWriter.writeDeferredName(JsonWriter.java:401)
at com.google.gson.stream.JsonWriter.value(JsonWriter.java:495)
at com.google.gson.internal.bind.TypeAdapters$7.write(TypeAdapters.java:246)
at com.google.gson.internal.bind.TypeAdapters$7.write(TypeAdapters.java:231)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:91)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:206)
at com.google.gson.Gson$FutureTypeAdapter.write(Gson.java:894)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:91)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:206)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:91)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:206)
at com.google.gson.Gson$FutureTypeAdapter.write(Gson.java:894)

造成这种情况的原因是什么？