Spring Boot MockMvc 测试中如何传递请求体对象？

// src/main/java/com/example/demo/dto/CartDto.java
package com.example.demo.dto;

import java.util.Objects;

public class CartDto {
    private String itemId;
    private int quantity;

    public CartDto() {
    }

    public CartDto(String itemId, int quantity) {
        this.itemId = itemId;
        this.quantity = quantity;
    }

    // Getters and Setters
    public String getItemId() {
        return itemId;
    }

    public void setItemId(String itemId) {
        this.itemId = itemId;
    }

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    @Override
    public String toString() {
        return "CartDto{" +
               "itemId='" + itemId + '\'' +
               ", quantity=" + quantity +
               '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        CartDto cartDto = (CartDto) o;
        return quantity == cartDto.quantity && Objects.equals(itemId, cartDto.itemId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(itemId, quantity);
    }
}

// src/main/java/com/example/demo/controller/UserController.java
package com.example.demo.controller;

import com.example.demo.dto.CartDto;
import com.example.demo.service.CartService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/user")
public class UserController {

    // 假设 CartService 处理业务逻辑
    @Autowired
    private CartService cartService;

    @PostMapping(value = "/addItemIntoCart", consumes = {"application/json"})
    public ResponseEntity<String> addItemToCart(@RequestBody CartDto cartDto) {
        System.out.println("Received CartDto: " + cartDto);
        // 调用服务层处理业务逻辑
        String result = cartService.addItemIntoCart(cartDto);
        return ResponseEntity.ok(result);
    }
}

// src/test/java/com/example/demo/controller/UserControllerTest.java
package com.example.demo.controller;

import com.example.demo.dto.CartDto;
import com.example.demo.service.CartService;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;

import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@WebMvcTest(UserController.class) // 专注于测试 Web 层，不加载完整的 Spring 应用上下文
public class UserControllerTest {

    @Autowired
    private MockMvc mockMvc; // MockMvc 实例，用于执行模拟请求

    @MockBean // 模拟 CartService，避免加载实际的业务逻辑和数据库依赖
    private CartService cartService;

    private ObjectMapper objectMapper; // 用于对象和 JSON 之间的转换

    @BeforeEach // JUnit 5 的 @BeforeEach，JUnit 4 对应 @Before
    void setUp() {
        objectMapper = new ObjectMapper(); // 初始化 ObjectMapper
        // 如果需要，可以在此处配置 ObjectMapper，例如禁用日期时间戳等
    }

    @Test
    void testAddItemIntoCart() throws Exception {
        // 1. 创建要作为请求体发送的 DTO 对象
        CartDto cartDto = new CartDto("PROD-001", 3);

        // 2. 使用 ObjectMapper 将 DTO 对象转换为 JSON 字符串
        String cartDtoJson = objectMapper.writeValueAsString(cartDto);

        // 3. 模拟 CartService 的行为，当调用 addItemIntoCart 时返回指定字符串
        when(cartService.addItemIntoCart(any(CartDto.class))).thenReturn("Item PROD-001 added to cart successfully.");

        // 4. 执行 MockMvc 请求
        mockMvc.perform(post("/user/addItemIntoCart") // 指定 POST 请求和 URL
                        .contentType(MediaType.APPLICATION_JSON) // 设置请求的 Content-Type 为 JSON
                        .content(cartDtoJson)) // 将 JSON 字符串作为请求体内容
                .andExpect(status().isOk()) // 验证 HTTP 状态码是否为 200 OK
                .andExpect(content().string("Item PROD-001 added to cart successfully.")) // 验证响应体内容
                .andReturn(); // 获取 MvcResult，如果需要进一步的断言
    }
}