惰性获取元素

Question

我使用join fetch query来获取公司和productSLA，因为公司有用户列表，并且它没有被初始化。因此，当我使用responseentity.ok发送响应时，它抛出了惰性初始化异常。我不想为了这个目的而想要用户列表，有没有什么方法可以把它发送到前端而不会产生惰性的init异常有人建议我使用dto来做这件事。

我在前端使用了angular。当我使用jsp时，我从来没有遇到过这样的问题。

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

 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer userId;

 @OneToMany(mappedBy = "user", cascade = CascadeType.ALL,fetch=FetchType.EAGER)
 private List<Ticket> raisedTickets;

 @NotNull
 @Column(unique = true)
 @Email(message = "Invalid Email")
 private String email;

 @NotNull
 @Column
 @Length(min = 4, max = 12, message = "First name must be between 4 to 12 character long")
 private String firstName;

 @NotNull
 @Column
 @Length(min = 4, max = 12, message = "Last name must be between 4 to 12 character long")
 private String lastName;

 @NotNull
 @Column
 @Length(min = 8, max = 100, message = "Password must be 4 to 12 character long")
 private String password;

 @NotNull
 @Column
 @Length(min = 3, max = 30, message = "Company Name must be between 3 to 12 character long")
 private String companyName;

 @Column(name = "USER_ROLE")
 @Enumerated(EnumType.STRING)
 private UserRolesEnum userRole;

 @ManyToOne
 @JoinColumn(name = "COMPANY_ID", nullable = false)
 @NotNull
 private Company company;

 @OneToMany(mappedBy="user", cascade=CascadeType.ALL)
 private List<ProductAssociated> productAssociatedList=new ArrayList<ProductAssociated>();

 public User() {
 }

 public User(String firstName, String lastName, String email, String password, String companyName,
   UserRolesEnum role) {
  super();
  this.firstName = firstName;
  this.lastName = lastName;
  this.email = email;
  this.password = password;
  this.companyName = companyName;
  this.userRole = role;
 }

 public Integer getUserId() {
  return userId;
 }

 public void setUserId(Integer id) {
  this.userId = id;
 }

 public List<Ticket> getRaisedTickets() {
  return raisedTickets;
 }
 public void setRaisedTickets(List<Ticket> raisedTickets) {
  this.raisedTickets = raisedTickets;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 public String getEmail() {
  return email;
 }

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

 public String getPassword() {
  return password;
 }

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

 public String getCompanyName() {
  return companyName;
 }

 public void setCompanyName(String companyName) {
  this.companyName = companyName;
 }

 public UserRolesEnum getUserRole() {
  return userRole;
 }

 public void setUserRole(UserRolesEnum userRole) {
  this.userRole = userRole;
 }

 public Company getCompany() {
  return company;
 }

 public void setCompany(Company company) {
  this.company = company;
 }

 public List<ProductAssociated> getProductAssociatedList() {
  return productAssociatedList;
 }

 public void setProductAssociatedList(List<ProductAssociated> productAssociatedList) {
  this.productAssociatedList = productAssociatedList;
 }

 public void addProductAssociated(ProductAssociated productAssociated) {
  productAssociatedList.add(productAssociated);
  productAssociated.setUser(this);
}  





    @Entity
@Table(name="PRODUCT_SLA")
public class ProductSLA {

 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 @Column(name="SLA_ID")
 private Integer slaId;

 @NotNull
 @Column(name="RESPONSE_TIME")
 private int responseTime;

 @Column(name="RESOLVE_TIME")
 private int resolveTime;

 @NotNull
 @Column(name="PRIORITY")
 @Enumerated(EnumType.STRING)
 private PriorityEnum priority;

 @ManyToOne
 @JoinColumn(name="COMPANY_ID", nullable = false)
 private Company company;

 @ManyToOne
 @JoinColumn(name="PRODUCT_ID", nullable = false)
 private Product product;

 public ProductSLA() {
  super();
 }

 public ProductSLA(Integer slaId, int responseTime, int resolveTime, PriorityEnum priority) {
  super();
  this.slaId = slaId;
  this.responseTime = responseTime;
  this.resolveTime = resolveTime;
  this.priority = priority;
 }

 public Integer getSlaId() {
  return slaId;
 }

 public void setSlaId(Integer slaId) {
  this.slaId = slaId;
 }

 public int getResponseTime() {
  return responseTime;
 }

 public void setResponseTime(int responseTime) {
  this.responseTime = responseTime;
 }

 public int getResolveTime() {
  return resolveTime;
 }

 public void setResolveTime(int resolveTime) {
  this.resolveTime = resolveTime;
 }

 public PriorityEnum getPriority() {
  return priority;
 }

 public void setPriority(PriorityEnum priority) {
  this.priority = priority;
 }

 public Company getCompany() {
  return company;
 }

 public void setCompany(Company company) {
  this.company = company;
 }

 public Product getProduct() {
  return product;
 }

 public void setProduct(Product product) {
  this.product = product;
 }

}



    @Entity
@Table(name = "COMPANY_TABLE")
public class Company {

 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 @Column(name = "COMPANY_ID")
 private Integer companyId;

 @NotNull
 @Column(name = "COMPANY_NAME", unique = true)
 private String companyName;

 @NotNull
 @Column(name = "ADDRESS_LINE1")
 private String addressLine1;

 @Column(name = "ADDRESS_LINE2")
 private String addressLine2;

 @NotNull
 @Column(name = "CITY")
 private String city;

 @NotNull

 @Column(name="STATE_NAME")

 private String state;

 @NotNull
 @Column(name = "COUNTRY")
 private String country;

 @NotNull
 @Column(name = "PHONE")
 private String phone;

 @NotNull
 @Column(name = "POSTAL_CODE")
 private String postalCode;

 @NotNull
 @Column(name = "COMPANY_WEBSITE")
 private String companyWebsite;

 @OneToMany( mappedBy = "company", cascade = CascadeType.ALL)
 private List<User> userList = new ArrayList<User>();

 @OneToMany(mappedBy = "product", cascade = CascadeType.ALL)
 private List<ProductSLA> productSLAList = new ArrayList<ProductSLA>();

 @OneToMany(mappedBy = "company", cascade = CascadeType.ALL, orphanRemoval=true)
 private List<AccessLevel> accessLevelList=new ArrayList<AccessLevel>();

 public Company() {
  super();
 }

 public Company(Integer companyId, String companyName, String addressLine1, String addressLine2, String city,
   String state, String country, String phone, String postalCode, String companyWebsite) {
  super();
  this.companyId = companyId;
  this.companyName = companyName;
  this.addressLine1 = addressLine1;
  this.addressLine2 = addressLine2;
  this.city = city;
  this.state = state;
  this.country = country;
  this.phone = phone;
  this.postalCode = postalCode;
  this.companyWebsite = companyWebsite;
 }

 public Integer getCompanyId() {
  return companyId;
 }

 public void setCompanyId(Integer companyId) {
  this.companyId = companyId;
 }

 public String getCompanyName() {
  return companyName;
 }

 public void setCompanyName(String companyName) {
  this.companyName = companyName;
 }

 public String getAddressLine1() {
  return addressLine1;
 }

 public void setAddressLine1(String addressLine1) {
  this.addressLine1 = addressLine1;
 }

 public String getAddressLine2() {
  return addressLine2;
 }

 public void setAddressLine2(String addressLine2) {
  this.addressLine2 = addressLine2;
 }

 public String getCity() {
  return city;
 }

 public void setCity(String city) {
  this.city = city;
 }

 public String getState() {
  return state;
 }

 public void setState(String state) {
  this.state = state;
 }

 public String getCountry() {
  return country;
 }

 public void setCountry(String country) {
  this.country = country;
 }

 public String getPhone() {
  return phone;
 }

 public void setPhone(String phone) {
  this.phone = phone;
 }

 public String getPostalCode() {
  return postalCode;
 }

 public void setPostalCode(String postalCode) {
  this.postalCode = postalCode;
 }

 public String getCompanyWebsite() {
  return companyWebsite;
 }

 public void setCompanyWebsite(String companyWebsite) {
  this.companyWebsite = companyWebsite;
 }

 public List<User> getUserList() {
  return userList;
 }

 public void setUserList(List<User> userList) {
  this.userList = userList;
 }

 public void addUser(User user) {
  userList.add(user);
  user.setCompany(this);
 }

 public List<ProductSLA> getProductSLAList() {
  return productSLAList;
 }

 public void setProductSLAList(List<ProductSLA> productSLAList) {
  this.productSLAList = productSLAList;
 }

 public void addProductSLA(ProductSLA productSLA) {
  productSLAList.add(productSLA);
  productSLA.setCompany(this);
 }


 public List<AccessLevel> getAccessLevelList() {
  return accessLevelList;
 }

 public void setAccessLevelList(List<AccessLevel> accessLevelList) {
  this.accessLevelList = accessLevelList;
 }

 public void addAccessLevel(AccessLevel accessLevel) {
  accessLevelList.add(accessLevel);
  accessLevel.setCompany(this);
 }
}

编辑我找到了解决方案，但我不知道该使用哪一个以及如何使用，因为有很多解决方案。Avoid Jackson serialization on non fetched lazy objects

Answer 1

假设你的hibernate会话已经在控制器中关闭了(这是一个合理的假设，因为我们不想在spring/hibernate层之外公开我们的hibernate会话)，如果你试图访问一个在会话内没有加载的集合，你就会遇到这种类型的问题。

好了！

我还假设您返回的是一个"hibernate托管实体“或集合，而不是DTO。我感觉到的是，当实体被转换成JSON时，所有的getter都会被底层框架调用，除非它们被标记为'ignore‘(或者类似的东西)。或者你的UI正在调用userList，这时它会抛出异常，因为hibernate返回了一个代理。

无论如何，最好返回一个DTO并以您喜欢的方式填充它。返回DTO (或DTO集合)比返回实体更可取的原因有很多。

Answer 2

为了解决这个问题，我使用了http消息转换器，

应用程序配置如下所示：

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.add(jacksonMessageConverter());
    super.configureMessageConverters(converters);
}

和

public MappingJackson2HttpMessageConverter jacksonMessageConverter(){
    MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();
    ObjectMapper mapper = new ObjectMapper();
    mapper.registerModule(new Hibernate5Module());
    messageConverter.setObjectMapper(mapper);
    return messageConverter;

}

需要依赖项

<dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-hibernate5</artifactId>
        <version>2.8.7</version>
    </dependency>

对于这个问题，如果您愿意修改每个getter方法，也有一个糟糕的解决方案：jackson 2 object to json ignore lazy loading