Spring Boot开发REST API：MySQL数据无法获取接口返回空白

我最近用Spring Boot开发REST API，代码运行无报错，但访问localhost:8080/expenses/时显示空白页面，不清楚原因。

实体类 #

import javax.persistence.*;
import java.math.BigDecimal;
import java.sql.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "tbl_expenses")
public class Expense {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name ="expense_name")
    private String name;


    private String description;


    @Column(name ="expense_amount")
    private BigDecimal amount;
    private String category;
    private Date date;

}

控制器类 #

package in.pranay.expensetrackerapi.controller;


import in.pranay.expensetrackerapi.entity.Expense;
import in.pranay.expensetrackerapi.service.ExpenseService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class ExpenseController {

    @Autowired
    private ExpenseService expenseService;

    @GetMapping("/expenses")
    public List<Expense> getAllExpenses() {
        return expenseService.getAllExpenses();
    }

}

Repository接口 #

package in.pranay.expensetrackerapi.repository;

import in.pranay.expensetrackerapi.entity.Expense;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface ExpenseRepository extends JpaRepository<Expense, Long> {
}

Application.properties配置 #

spring.datasource.url=jdbc:mysql://localhost:3306/expensetracker
spring.datasource.username=root
spring.datasource.password=pranay@1404

1. 修正请求路径匹配 #

控制器注解的路径是/expenses，但你访问的是/expenses/（多了末尾斜杠）。Spring默认严格匹配路径，直接访问localhost:8080/expenses测试。

2. 检查数据库数据 #

如果tbl_expenses表为空，接口会返回空数组[]，部分浏览器会显示空白。用SQL语句SELECT * FROM tbl_expenses;验证数据，或者在控制器方法中打印返回结果：

@GetMapping("/expenses")
public List<Expense> getAllExpenses() {
    List<Expense> expenses = expenseService.getAllExpenses();
    System.out.println("返回数据：" + expenses);
    return expenses;
}

若控制台输出[]，插入测试数据即可。

3. 确认Service层逻辑 #

检查ExpenseService是否正确调用Repository的findAll()方法：

@Service
public class ExpenseService {
    @Autowired
    private ExpenseRepository expenseRepository;

    public List<Expense> getAllExpenses() {
        return expenseRepository.findAll();
    }
}

若Service返回null，接口会显示空白。

4. 完善数据库配置 #

当前配置缺少驱动和Hibernate参数，补充以下内容：

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

确保MySQL服务启动、数据库expensetracker已创建、账号密码正确。

5. 验证依赖与日志 #

确认Lombok依赖已添加（实体类用了@Data注解），启动时查看控制台日志，排查数据库连接失败、实体映射错误等隐性异常。

内容的提问来源于stack exchange，提问作者Pranay Sahu