Question

首先，让我解释一下我的用例。它很直接。有一个用户实体和一个服务实体。我使用UserService作为连接实体（连接表）在User和Service之间有很多关联。最初，会有一些用户和一些服务集。用户可以随时订阅任何服务。在这种情况下，将向UserService添加一个条目。但是，当我试图创建一个新的UserService关联时，我得到空指针异常。我可以单独创建用户和服务。

我的实体是： User.java

package dao.models;

import java.io.Serializable;
import javax.persistence.*;

import com.fasterxml.jackson.annotation.JsonBackReference;
@Entity
@org.hibernate.annotations.Proxy(lazy=false)
@Table(name="`user`", schema="emm")
public class User implements Serializable {
    public User() {
    }

    @Column(name="id", nullable=false, unique=true) 
    @Id 
    @GeneratedValue(generator="EMM_USER_ID_GENERATOR")  
    @org.hibernate.annotations.GenericGenerator(name="EMM_USER_ID_GENERATOR", strategy="native")    
    private long id;


    @ManyToOne(targetEntity=dao.models.Tenant.class, fetch=FetchType.LAZY)  
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.LOCK})    
    @JoinColumns({ @JoinColumn(name="tenant_id", referencedColumnName="id", nullable=false) })  
    @org.hibernate.annotations.LazyToOne(value=org.hibernate.annotations.LazyToOneOption.NO_PROXY)  
    private dao.models.Tenant tenant;

    @OneToOne(targetEntity=dao.models.Person.class, fetch=FetchType.LAZY)   
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @JoinColumns({ @JoinColumn(name="Person_id", nullable=false) }) 
    @org.hibernate.annotations.LazyToOne(value=org.hibernate.annotations.LazyToOneOption.NO_PROXY)  
    private dao.models.Person person;

    @Column(name="password", nullable=true, length=255) 
    private String password;

    @Column(name="email", nullable=false, length=255)   
    private String email;

    @Column(name="status", nullable=true, length=255)   
    private String status;

    @ManyToMany(mappedBy="user", targetEntity=dao.models.TenantGroup.class) 
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.TenantGroup> group = new java.util.ArrayList<dao.models.TenantGroup>();

    @OneToMany(mappedBy="user", targetEntity=dao.models.UserService.class)  
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.UserService> userService = new java.util.ArrayList<dao.models.UserService>();

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

    public long getId() {
        return id;
    }



    public void setPassword(String value) {
        this.password = value;
    }

    public String getPassword() {
        return password;
    }

    public void setEmail(String value) {
        this.email = value;
    }

    public String getEmail() {
        return email;
    }

    public void setStatus(String value) {
        this.status = value;
    }

    public String getStatus() {
        return status;
    }

    public void setTenant(dao.models.Tenant value) {
        this.tenant = value;
    }

    public dao.models.Tenant getTenant() {
        return tenant;
    }

    public void setPerson(dao.models.Person value) {
        this.person = value;
    }

    public dao.models.Person getPerson() {
        return person;
    }

    public void setGroup(java.util.List<dao.models.TenantGroup> value) {
        this.group = value;
    }

    public java.util.List<dao.models.TenantGroup> getGroup() {
        return group;
    }




    public java.util.List<dao.models.UserService> getUserService() {
        return userService;
    }

    public void setUserService(
            java.util.List<dao.models.UserService> userService) {
        this.userService = userService;
    }

    public String toString() {
        return String.valueOf(getId());
    }

}

服务实体

package dao.models;

import java.io.Serializable;
import javax.persistence.*;

import com.fasterxml.jackson.annotation.JsonBackReference;
@Entity
@org.hibernate.annotations.Proxy(lazy=false)
@Table(name="service", schema="emm")
public class Service implements Serializable {
    public Service() {
    }

    @Column(name="service_id", nullable=false, unique=true) 
    @Id 
    @GeneratedValue(generator="EMM_SERVICE_SERVICE_ID_GENERATOR")   
    @org.hibernate.annotations.GenericGenerator(name="EMM_SERVICE_SERVICE_ID_GENERATOR", strategy="native") 
    private long id;

    @Column(name="service_name", nullable=false, length=255)    
    @org.hibernate.annotations.Index(name="service_service_name")   
    private String serviceName;

    @Column(name="description", nullable=true, length=255)  
    private String description;

    @Column(name="app_key", nullable=false, length=255) 
    private String appKey;

    @Column(name="app_token", nullable=false, length=255)   
    private String appToken;

    @Column(name="learnmoreurl",  length=255)   
    private String learnMoreURL;

    @Column(name="trialurl",  length=255)   
    private String trialURL;

    @ManyToMany(mappedBy="service", targetEntity=dao.models.Device.class)   
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.Device> device = new java.util.ArrayList<dao.models.Device>();

    @OneToMany(mappedBy="service", targetEntity=dao.models.ServiceParam.class)  
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.DELETE})   
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.ServiceParam> serviceParams = new java.util.ArrayList<dao.models.ServiceParam>();

    @OneToMany(mappedBy="service", targetEntity=dao.models.TenantService.class) 
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.PERSIST, org.hibernate.annotations.CascadeType.MERGE,
                                        org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.DELETE_ORPHAN})    
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.TenantService> tenantService = new java.util.ArrayList<dao.models.TenantService>();

    @OneToMany(mappedBy="service", targetEntity=dao.models.UserService.class)   
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.DELETE})   
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.UserService> userService = new java.util.ArrayList<dao.models.UserService>();

    public long getId() {
        return id;
    }

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

    public String getServiceName() {
        return serviceName;
    }


    public void setServiceName(String serviceName) {
        this.serviceName = serviceName;
    }

    public String getDescription() {
        return description;
    }

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

    public String getAppKey() {
        return appKey;
    }

    public void setAppKey(String appKey) {
        this.appKey = appKey;
    }

    public String getAppToken() {
        return appToken;
    }

    public void setAppToken(String appToken) {
        this.appToken = appToken;
    }

    public String getLearnMoreURL() {
        return learnMoreURL;
    }
    public void setLearnMoreURL(String learnMoreURL) {
        this.learnMoreURL = learnMoreURL;
    }

    public String getTrialURL() {
        return trialURL;
    }

    public void setTrialURL(String trialURL) {
        this.trialURL = trialURL;
    }

    public java.util.List<dao.models.Device> getDevice() {
        return device;
    }


    public void setDevice(java.util.List<dao.models.Device> device) {
        this.device = device;
    }

    public java.util.List<dao.models.ServiceParam> getServiceParams() {
        return serviceParams;
    }

    public void setServiceParams(
            java.util.List<dao.models.ServiceParam> serviceParams) {
        this.serviceParams = serviceParams;
    }

    public java.util.List<dao.models.TenantService> getTenantService() {
        return tenantService;
    }

    public void setTenantService(
            java.util.List<dao.models.TenantService> tenantService) {
        this.tenantService = tenantService;
    }

    public java.util.List<dao.models.UserService> getUserService() {
        return userService;
    }

    public void setUserService(
            java.util.List<dao.models.UserService> userService) {
        this.userService = userService;
    }
    public String toString() {
        return String.valueOf(getId());
    }

}

最后是加入实体

UserService.java

package dao.models;

import java.io.Serializable;
import javax.persistence.*;
@Entity
@org.hibernate.annotations.Proxy(lazy=false)
@Table(name="user_service" ,schema="emm")
public class UserService implements Serializable {
    public UserService() {
    }

    @Column(name="id", nullable=false, unique=true) 
    @Id 
    @GeneratedValue(generator="EMM_USER_SERVICE_ID_GENERATOR")  
    @org.hibernate.annotations.GenericGenerator(name="EMM_USER_SERVICE_ID_GENERATOR", strategy="native")    
    private long id;

    @ManyToOne(targetEntity=dao.models.User.class, fetch=FetchType.LAZY)    
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.LOCK})    
    @JoinColumns({ @JoinColumn(name="user_id", referencedColumnName="id", nullable=false) })    
    @org.hibernate.annotations.LazyToOne(value=org.hibernate.annotations.LazyToOneOption.NO_PROXY)  
    private dao.models.User user;

    @ManyToOne(targetEntity=dao.models.Service.class, fetch=FetchType.LAZY) 
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.LOCK})    
    @JoinColumns({ @JoinColumn(name="service_id", referencedColumnName="service_id", nullable=false) }) 
    @org.hibernate.annotations.LazyToOne(value=org.hibernate.annotations.LazyToOneOption.NO_PROXY)  
    private dao.models.Service service;

    @Column(name="param_name", nullable=false)  
    private String paramName;

    @Column(name="param_value", nullable=true)  
    private String paramValue;

    @OneToMany(mappedBy="userService", targetEntity=dao.models.UserServiceToken.class)  
    @org.hibernate.annotations.Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.LOCK}) 
    @org.hibernate.annotations.LazyCollection(org.hibernate.annotations.LazyCollectionOption.TRUE)  
    private java.util.List<dao.models.UserServiceToken> userServiceToken = new java.util.ArrayList<dao.models.UserServiceToken>();



    public long getId() {
        return id;
    }



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



    public dao.models.User getUser() {
        return user;
    }



    public void setUser(dao.models.User user) {
        this.user = user;
    }



    public dao.models.Service getService() {
        return service;
    }



    public void setService(dao.models.Service service) {
        this.service = service;
    }



    public String getParamName() {
        return paramName;
    }



    public void setParamName(String paramName) {
        this.paramName = paramName;
    }



    public String getParamValue() {
        return paramValue;
    }



    public void setParamValue(String paramValue) {
        this.paramValue = paramValue;
    }



    public java.util.List<dao.models.UserServiceToken> getUserServiceToken() {
        return userServiceToken;
    }



    public void setUserServiceToken(
            java.util.List<dao.models.UserServiceToken> userServiceToken) {
        this.userServiceToken = userServiceToken;
    }



    public String toString() {
        return String.valueOf(getId());
    }

}

现在我的问题，GET请求正常工作，但是，当我尝试创建一个新的UserService时，我得到空指针异常。

POST：http://localhost:8080/em/api/userServices/ 我试图将用户1与服务2相关联要求：

{
    "paramName": "p1",
    "paramValue": "v1",
    "service": {
        "href": `"http://localhost:8080/em/api/userServices/1/service/2"`
    },
    "user": {
        "href": `"http://localhost:8080/em/api/userServices/1/user/1"`
    }
}

错误Messgae：

{
    "cause": {
        "cause": {
            "cause": null,
            "message": null
        },
        "message": "(was java.lang.NullPointerException) (through reference chain: dao.models.UserService[\"service\"])"
    },
    "message": "Could not read JSON: (was java.lang.NullPointerException) (through reference chain: dao.models.UserService[\"service\"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: dao.models.UserService[\"service\"])"
}

GET http://localhost:8080/em/api/userServices产生以下输出：

{
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/em/api/userServices{?page,size,sort}",
      "templated" : true
    }
  },
  "_embedded" : {
    "userServices" : [ {
      "paramName" : "p1",
      "paramValue" : "v1",
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/em/api/userServices/1"
        },
        "userServiceToken" : {
          "href" : "http://localhost:8080/em/api/userServices/1/userServiceToken"
        },
        "user" : {
          "href" : "http://localhost:8080/em/api/userServices/1/user"
        },
        "service" : {
          "href" : "http://localhost:8080/em/api/userServices/1/service"
        }
      }
    }, {
      "paramName" : "pone",
      "paramValue" : "vone",
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/em/api/userServices/2"
        },
        "userServiceToken" : {
          "href" : "http://localhost:8080/em/api/userServices/2/userServiceToken"
        },
        "user" : {
          "href" : "http://localhost:8080/em/api/userServices/2/user"
        },
        "service" : {
          "href" : "http://localhost:8080/em/api/userServices/2/service"
        }
      }
    } ]
  },
  "page" : {
    "size" : 20,
    "totalElements" : 2,
    "totalPages" : 1,
    "number" : 0
  }
}

是否有人使用Spring-data-rest成功实现了ManyToMany关联。如果是这样，请在这方面帮助我

Answer 1

我找出了问题，并让它发挥作用。

以前，我的要求是：

{
    "paramName": "p1",
    "paramValue": "v1",
    "service": {
        "href": "http://localhost:8080/em/api/userServices/1/service/2"
    },
    "user": {
        "href": "http://localhost:8080/em/api/userServices/1/user/1"
    }
}

我发现它应该是以下内容：

{
    "paramName": "p1",
    "paramValue": "v1",
    "service":  "http://localhost:8080/em/api/services/2",
    "user":  "http://localhost:8080/em/api/users/1"
 }

我觉得spring-data-rest仍然存在问题。如果有人不这么认真，请澄清一下。即使有固定的请求，我也得到了ServiceId的空约束。我在db中发现，服务的主键列是service_id。即使我有正确的实体映射（服务实体中的我的Id属性正确映射到db中的service_id），它也无法工作，我不得不将列名更改为id以使其正常工作。

Spring-Data-Rest应该依赖于Id的实体映射吗？如果是这样，那么仍有一个错误。

谢谢，的Vivek

Spring Data Rest ManytoMany POST

1 个答案: