Question

我使用Java / Spring网络应用程序，它包含3个实体。下面提供了MySQL模式，

正如我们所见，有3个实体和各自的用户表，status和wallet_info。下面提供了3个实体，

@Entity
@Table(name = "wallet_info")
public class WalletInfo {

@Id
@Column(name = "id", unique = true, nullable = false)
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@NotNull
@Column(name = "code")
private String code;

@NotNull
@Column(name = "address")
private String address;

@NotNull
@Column(name = "currency")
private String currency;

@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "wallet_id")
Set<Status> statuses = new HashSet<>(0);

public Long getId() {
    return id;
}

public WalletInfo(@NotNull String name, @NotNull String address, @NotNull String currency) {
    this.code = name;
    this.address = address;
    this.currency = currency;
}

public WalletInfo(@NotNull String name, @NotNull String address) {
    this.code = name;
    this.address = address;
}

public WalletInfo() {
}

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

public String getCode() {
    return code;
}

public void setCode(String code) {
    this.code = code;
}

public String getAddress() {
    return address;
}

public void setAddress(String address) {
    this.address = address;
}

public String getCurrency() {
    return currency;
}

public void setCurrency(String currency) {
    this.currency = currency;
}

public Set<Status> getStatuses() {
    return statuses;
}

public void setStatuses(Set<Status> statuses) {
    this.statuses = statuses;
}

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof WalletInfo)) return false;

    WalletInfo that = (WalletInfo) o;

    if (!getId().equals(that.getId())) return false;
    if (!getCode().equals(that.getCode())) return false;
    if (!getAddress().equals(that.getAddress())) return false;
    return getCurrency().equals(that.getCurrency());
}

@Override
public int hashCode() {
    int result = getId().hashCode();
    result = 31 * result + getCode().hashCode();
    result = 31 * result + getAddress().hashCode();
    result = 31 * result + getCurrency().hashCode();
    return result;
}

@Override
public String toString() {

    return "WalletInfo{" +
            "id=" + id +
            ", code='" + code + '\'' +
            ", address='" + address + '\'' +
            ", currency='" + currency + '\'' +
            '}';
}
}




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

@Id
@Column(name = "id", unique = true, nullable = false)
@NotNull
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;

@NotNull
@Column(name = "name")
@Size(min = 5, max = 45, message = "Name must be between 5 and 45 characters.")
private String name;

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "user_id")
Set<Status> statuses = new HashSet<Status>(0);

public User() {

}

public User(int id, String name) {
    super();
    this.id = id;
    this.name = name;
}

public User(String name) {
    this.name = name;
}

public int getId() {
    return id;
}

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

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Set<Status> getStatuses() {
    return statuses;
}

public void setStatuses(Set<Status> statuses) {
    this.statuses = statuses;
}

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof User)) return false;

    User user = (User) o;

    if (getId() != user.getId()) return false;
    return getName().equals(user.getName());
}

@Override
public int hashCode() {
    int result = getId();
    result = 31 * result + getName().hashCode();
    return result;
}

@Override
public String toString() {
    return "User{" +
            "id=" + id +
            ", name='" + name + '\'' +
            '}';
   }
  }



@Entity
@Table(name = "status")
public class Status {

    @Id
    @Column(name = "id", unique = true, nullable = false)
    @NotNull
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

@NotNull
@Column(name = "balance")
private float balance;

@NotNull
@Column(name = "address")
@Size(min = 5, max = 90, message = "Address must be between 5 and 90 characters.")
private String address;

@NotNull
@Column(name = "transaction")
@Size(min = 5, max = 90, message = "Transaction history must be between 5 and 90 characters.")
private String transaction;

@NotNull
@Column(name = "user_id")
@JoinColumn(table = "user", name = "id", nullable = false)
private int user_id;

@NotNull
@JoinColumn(name = "id", table = "wallet_id", nullable = false)
@Column(name = "wallet_id")
private long wallet_id;

public Status() {

}

public Status(float balance, String transaction, String address, int user_id) {
    this.user_id = user_id;
    this.balance = balance;
    this.address = address;
    this.transaction = transaction;
}

public Status(int id, int user_id, float balance, String address, String transaction) {
    super();
    this.id = id;
    this.user_id = user_id;
    this.balance = balance;
    this.address = address;
    this.transaction = transaction;
}

public int getId() {
    return id;
}


public int getUser_id() {
    return user_id;
}

public float getBalance() {
    return balance;
}

public String getAddress() {
    return address;
}

public String getTransaction() {
    return transaction;
}

public long getWallet_id() {
    return wallet_id;
}

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

public void setUser_id(int user_id) {
    this.user_id = user_id;
}

public void setBalance(float balance) {
    this.balance = balance;
}

public void setAddress(String address) {
    this.address = address;
}

public void setTransaction(String transaction) {
    this.transaction = transaction;
}

public void setWallet_id(long wallet_id) {
    this.wallet_id = wallet_id;
}

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof Status)) return false;

    Status status = (Status) o;

    if (id != status.id) return false;
    if (user_id != status.user_id) return false;
    if (Float.compare(status.balance, balance) != 0) return false;
    if (!address.equals(status.address)) return false;
    return transaction.equals(status.transaction);
}

@Override
public int hashCode() {
    int result = id;
    result = 31 * result + user_id;
    result = 31 * result + (balance != +0.0f ? Float.floatToIntBits(balance) : 0);
    result = 31 * result + address.hashCode();
    result = 31 * result + transaction.hashCode();
    return result;
}

@Override
public String toString() {
    return "Status{" +
            "id=" + id +
            ", user_id=" + user_id +
            ", balance=" + balance +
            ", address='" + address + '\'' +
            ", transaction='" + transaction + '\'' +
            '}';
    }
}

当我命令使用cURL curl -X GET http://localhost:8080/rest/wallet/wallets | json时，我得到了outoput，

[

     {
    "id": 63,
    "code": "BTC",
    "address": "n2F2QEKk6Fqqk2yMTope5MYp1RtpT949ke",
    "currency": "Bitcoin",
    "statuses": []
  },
  {
    "id": 64,
    "code": "BTC",
    "address": "mrkdfp6qoVN3YiyJhq6nXPvgr3f7YpkS9j",
    "currency": "Bitcoin",
    "statuses": []
  },
  {
    "id": 65,
    "code": "BTC",
    "address": "n3VGaHLFx8KkpNDNHsGGcHWgMWyUoA3Qdm",
    "currency": "Bitcoin",
    "statuses": []
  }, 

  // some data 

]

终端没有错误，但statuses作为空列表。在WalletInfo课程中，当我更改FetchType

的LAZY时

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "wallet_id")
    Set<Status> statuses = new HashSet<>(0);

我收到错误消息

100   404    0   404    0     0    760      0 --:--:-- --:--:-- --:--:--   760
json: error: input is not JSON: Expected ':' instead of '}' at line 7, column 1:
        } ]{
        ^
[ {
  "id" : 1,
  "code" : "BTC",
  "address" : "mp51mPC38Wtcmybdyd9MPEB2bKnw6eYbCs",
  "currency" : "Bitcoin",
  "statuses"
} ]{
  "msg" : "failed to lazily initialize a collection of role: mobi.puut.entities.WalletInfo.statuses, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]->mobi.puut.entities.WalletInfo[\"statuses\"])",
  "date" : "2017-09-06T03:53:052Z"
}

为什么FetchType.LAZY和FetchType.EAGER会产生这种差异？

懒惰地初始化角色集合失败

0 个答案: