HttpMessageNotWritableException:No converter found for return value of type: class java.util.HashMap

深藏阁楼爱情的钟 2022-12-10 07:28 131阅读 0赞

请求springmvc中的接口时服务端出现`24-Sep-2020 20:08:51.902 警告 [http-nio-8080-exec-18] org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.logException Resolved [org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class java.util.HashMap]`，相关代码如下：

@ResponseBody
    @GetMapping("/ajaxAddItem/{id}")
    public Map<String, Object> ajaxAddItem(@PathVariable("id") Integer bookId, HttpServletRequest request) { 
        Book book = bookService.queryBookById(bookId);
        CartImpl cart = (CartImpl)request.getSession().getAttribute("cart");
        if (cart == null) { 
            cart = new CartImpl();
            request.getSession().setAttribute("cart", cart);
        }
        cart.addItem(new CartItem(book.getId(), book.getName(), 1, book.getPrice()));
        request.getSession().setAttribute("lastAddBook", book.getName());
    
        Map<String, Object> result = new HashMap<>();
        result.put("lastAddBook", book.getName());
        result.put("cartCount", cart.getTotalCount());
        return result;
    }

出现此问题的原因是使用了jackson中的功能(@ResponseBody)但是缺少了部分jar包，导入以下maven依赖即可(全都要)：

<dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson.version}</version>
    </dependency>