Spring Boot测试报错：JSON Path "$.echo"无值及404问题求助

核心报错 #

java.lang.AssertionError: No value at JSON path "$.echo"

控制台输出 #

MockHttpServletResponse:
           Status = 404
    Error message = null
          Headers = [Vary:"Origin", "Access-Control-Request-Method", "Access-Control-Request-Headers"]
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

问题说明 #

已搜索JsonPath相关问题并做修改，但问题仍未解决。已实现Service层，但测试时依然返回404，且JsonPath断言失败。

相关代码 #

测试类 #

package com.hackerrank.sample;

import com.hackerrank.sample.dto.StringResponse;
import com.hackerrank.sample.service.HelloService;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.test.annotation.DirtiesContext;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.web.servlet.MockMvc;

import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;


@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
@DirtiesContext(classMode = DirtiesContext.ClassMode.BEFORE_EACH_TEST_METHOD)
@AutoConfigureMockMvc
public class SampleApplicationTests {
    @Autowired
    private MockMvc mockMvc;

    @MockBean
    HelloService helloService;

    @Before
    public void setup() {

    }

    @Test
    public void defaultHelloTest() throws Exception {
        when(helloService.getDefaultHello()).thenReturn(new StringResponse("Hello World!"));
        mockMvc.perform(get("/defaultHello"))
                .andDo(print())
                .andExpect(jsonPath("$.echo").value("Hello World!"))
                .andExpect(
                        status().isOk());
    }
}

Controller类 #

package com.hackerrank.sample.controller;

import com.hackerrank.sample.dto.StringResponse;
import com.hackerrank.sample.service.HelloService;
import org.springframework.web.bind.annotation.*;

@RestController
public class SampleController {

    HelloService helloService;

    public SampleController(HelloService service) {
        this.helloService = service;
    }

    @GetMapping(value = {"/defaultHello/{message}"})
    public StringResponse getDefaultHello(@PathVariable String message) {
        return helloService.getDefaultHello(message);
    }

    @GetMapping(value = {"/defaultHello"})
    public StringResponse getDefaultHello() {
        return helloService.getDefaultHello();
    }

}

Service接口 #

package com.hackerrank.sample.service;

import com.hackerrank.sample.dto.StringResponse;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;
@Repository
public interface HelloService {
    public StringResponse getDefaultHello();
    public StringResponse getDefaultHello(String message);
}

Service实现类 #

package com.hackerrank.sample.service;

import com.hackerrank.sample.dto.StringResponse;
import org.springframework.stereotype.Service;

@Service
public class HelloServiceImpl implements HelloService {

    private StringResponse stringResponse;


    public HelloServiceImpl(StringResponse stringResponse) {
        this.stringResponse = stringResponse;
    }

    @Override
    public StringResponse getDefaultHello() {
        return new StringResponse("Hello World!");
    }

    @Override
    public StringResponse getDefaultHello(String message) {
        return new StringResponse("Hello + " + message);
    }
}

问题分析与解决办法 #

核心问题 #

控制台返回404是因为Spring无法正确创建HelloServiceImpl实例，导致SampleController无法被初始化注册，请求找不到对应接口。进而因为没有响应体，JsonPath断言$.echo自然找不到值，抛出错误。

具体原因：

1. HelloServiceImpl的构造函数依赖StringResponse，但StringResponse是普通DTO，未被Spring注册为Bean，Spring无法注入该依赖，导致Service实例创建失败。
2. HelloService接口错误标注了@Repository注解，该注解用于数据访问层，不适合标注在业务Service接口上。

修复步骤 #

1. 修改HelloServiceImpl构造函数：移除对StringResponse的依赖，因为实现代码中并未使用该成员变量，直接改为无参构造：

@Service
public class HelloServiceImpl implements HelloService {

    public HelloServiceImpl() {
    }

    @Override
    public StringResponse getDefaultHello() {
        return new StringResponse("Hello World!");
    }

    @Override
    public StringResponse getDefaultHello(String message) {
        return new StringResponse("Hello + " + message);
    }
}

2. 修正HelloService接口的注解：移除错误的@Repository和@Service注解，业务接口无需额外标注Spring注解：

package com.hackerrank.sample.service;

import com.hackerrank.sample.dto.StringResponse;

public interface HelloService {
    StringResponse getDefaultHello();
    StringResponse getDefaultHello(String message);
}

3. （可选）确保Controller依赖注入正常：如果你的Spring版本低于4.3，需要给SampleController的构造函数添加@Autowired注解，高版本可省略，但添加后兼容性更好：

@RestController
public class SampleController {

    HelloService helloService;

    @Autowired
    public SampleController(HelloService service) {
        this.helloService = service;
    }

    // 其余代码不变
}

完成以上修改后，Spring能正常创建Service和Controller实例，请求会匹配到对应的接口，返回正确的JSON响应，JsonPath断言也能正常执行。

内容的提问来源于stack exchange，提问作者Sgr