无法将“java.lang.String”类型的属性值转换为属性“transactions”所需的类型“java.util.List”

Question

我正在使用 thymeleaf 并在将数据从字符串转换为列表时遇到一些错误。 在这里我附上了我的代码

我的实体类：

@Entity
@Table(name="customer")
public class Customer {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;

@Column(name = "first_name")
@NotNull(message = "First Name cannot be empty")
@Size(min = 1, message = "First Name cannot be empty")
private String firstName;

@Column(name = "last_name")
@NotNull(message = "Last Name cannot be empty")
@Size(min = 1, message = "Last Name cannot be empty")
private String lastName;

@Column(name = "email")
@NotNull(message = "Email ID cannot be empty")
@Pattern(regexp = "^[a-zA-Z0-9.+_-]+@[a-zA-Z0-9.-]+$",
        message = "Enter valid mail id")
private String email;

@Column(name = "branch")
@NotNull(message = "Branch name cannot be empty")
private String branch;

@Column(name = "balance")
private double balance;

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumn(name = "customer_id")
private List<Transaction> transactions;

public Customer(String firstName, String lastName, String email, String branch, double balance) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.email = email;
    this.branch = branch;
    this.balance = balance;
}

public Customer() {
}

public int getId() {
    return id;
}

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

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 getBranch() {
    return branch;
}

public void setBranch(String branch) {
    this.branch = branch;
}

public double getBalance() {
    return balance;
}

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

public List<Transaction> getTransactions() {
    return transactions;
}

public void setTransactions(List<Transaction> transactions) {
    this.transactions = transactions;
}

public void addTransaction(Transaction transaction){
    if(transaction == null) {
        transactions = new ArrayList<>();
    }
    transactions.add(transaction);
}

@Override
public String toString() {
    return "Customer{" +
            "id=" + id +
            ", firstName='" + firstName + '\'' +
            ", lastName='" + lastName + '\'' +
            ", email='" + email + '\'' +
            ", branch='" + branch + '\'' +
            ", balance=" + balance +
            '}';
  }


@Entity
@Table(name = "transactions")
public class Transaction {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;

@Column(name = "transaction")
private double amount;

public Transaction() {
}

public Transaction(double amount) {
    this.amount = amount;
}

public int getId() {
    return id;
}

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

public double getAmount() {
    return amount;
}

public void setAmount(double amount) {
    this.amount = amount;
}

@Override
public String toString() {
    return "Transaction{" +
            "id=" + id +
            ", amount=" + amount +
            '}';
}

html格式：

    <h3>Customer Directory</h3>
    <hr>

    <p class="h4 mb-4">Save Customer</p>

    <form action="#" th:action="@{/customers/saveCustomer}"
          th:object="${customer}" method="POST">

        <!-- Add hidden form field to handle the update -->
        <input type="hidden" th:field="*{id}" />

        <input type="text" th:field="*{firstName}"
            class="form-control mb-4 col-4" placeholder="First Name">

        <input type="text" th:field="*{lastName}"
               class="form-control mb-4 col-4" placeholder="Last Name">

        <input type="text" th:field="*{email}"
               class="form-control mb-4 col-4" placeholder="Email">

        <input type="text" th:field="*{branch}"
               class="form-control mb-4 col-4" placeholder="Branch">

        <input type="text" th:field="*{balance}"
               class="form-control mb-4 col-4" placeholder="Balance">

        <input type="text" th:field="*{transactions}"
               class="form-control mb-4 col-4" placeholder="Transactions">

        <!--input type="hidden" th:field="*{transactions}" /-->

        <button type="submit" class="btn btn-info col-2">Save</button>

    </form>

    <hr>
    <a th:href="@{/customers/list}">Back to Customers List</a>

</div>

错误：

object='customer' 验证失败。 错误计数：1 org.springframework.validation.BindException：org.springframework.validation.BeanPropertyBindingResult：1 个错误字段“交易”对象“客户”中的字段错误：拒绝值 [[Transaction{id=1, amount=1000.0},交易{id=3，金额=100.0}]]； 代码 [typeMismatch.customer.transactions,typeMismatch.transactions,typeMismatch.java.util.List,typeMismatch]; 参数 [org.springframework.context.support.DefaultMessageSourceResolvable: 代码 [customer.transactions,transactions]; 参数 []; 默认消息[交易]]； 默认消息 [无法将“java.lang.String”类型的属性值转换为属性“transactions”所需的类型“java.util.List”； 嵌套异常是 org.springframework.core.convert.ConversionFailedException：无法从类型 [java.lang.String] 转换为类型 [@javax.persistence.OneToMany @javax.persistence.JoinColumn com.kaneki.springboot.bankapplication.entity。交易] 为值 '[Transaction{id=1, amount=1000.0}, Transaction{id=3, amount=100.0}]'; 嵌套异常是 java.lang.NumberFormatException：对于输入字符串：“[Transaction{id=1, amount=1000.0}, Transaction{id=3, amount=100.0}]”]

Answer 1

从您的 HTML 中，您将接收交易字段作为字符串，因此在控制器中您必须处理该字符串并从中提取 id 和金额，然后将该 id 和金额设置为交易表。 试试这个，如果你已经尝试过或在你的控制器中写过，请分享控制器的代码。