Springmvc接收前端传来的json数据时报错（415）解决方案（带了SSM常用的maven依赖）

今天使用$.post()方法返回json字符串时，报错，一搜是因为$.post()是$.ajax()的post请求的简化版没有

contentType:'application/json'

和后台数据格式对不上，行我该用了$.ajax()方法

$.ajax({
                    type: "post",
                    url: "${pageContext.request.contextPath}/add",
                    contentType:'application/json',
                    data: JSON.stringify(data.field),
                    dataType: "json",
                    success: function(data){
                    }
                });

 可是后台还是没有显示值，行我再搜发现

springmvc中要使用@RequestBody来让实体类封装前端传来的json数据

行，我改，但一连串的报错蜂拥而至，好！！我挨个看发现要在@RequestMapping中加入

consumes = "application/json"                 变成
@RequestMapping(value = "/add",consumes = "application/json")

好吧，我学的不精，改遭。              结果测了一晚上，还报错！！！！！！

测了又测，搜了又搜，经历了一个多小时，四五十页的浏览，发现TM的要用

jackson 的jar包，我导入了 fastjson 的jar包，就没有管 jackson 的，气死个人，下面总结一下Springmvc接收前端传来的json数据时的问题

 1.要在$.ajax中添加contentType:"application/json"

让前后台传递的编码一致

$.ajax({
       type: "post",
       url: "${pageContext.request.contextPath}/add",
       contentType:'application/json',
       data: JSON.stringify(data.field),
       dataType: "json",
       success: function(data){
       }
});

2.在Controller中方法的参数上加@RequestBody

可以不加@RequestMapping(value = "/add",consumes = "application/json")中的consumes = "application/json"

    @RequestMapping(value = "/add")
    @ResponseBody
    public String add(@RequestBody User user){
        System.out.println(user);
        return "ok";
    }

 3.最最最最最重要的是要看看配置文件和maven依赖配置好没有

jackson依赖

        
            com.fasterxml.jackson.core
            jackson-databind
            2.9.8
        
        
            com.fasterxml.jackson.core
            jackson-core
            2.9.8
        
        
            com.fasterxml.jackson.core
            jackson-annotations
            2.9.8
        

我SSM框架的maven依赖

ssm框架烦烦烦烦，springbootYYDS

    4.0.0

    org.example
    ssmbuild
    pom
    1.0-SNAPSHOT
    
        school-01
        school-02
        school-03
        school-04-system
    

    
        8
        8
    
    
    
        
            com.fasterxml.jackson.core
            jackson-databind
            2.9.8
        
        
            com.fasterxml.jackson.core
            jackson-core
            2.9.8
        
        
            com.fasterxml.jackson.core
            jackson-annotations
            2.9.8
        

        
        
            com.github.pagehelper
            pagehelper
            5.1.6
        


        
        
            org.mybatis.generator
            mybatis-generator-core
            1.3.7
        


        
            
                commons-fileupload
                commons-fileupload
                1.3.3
            

            
                javax.servlet
                javax.servlet-api
                4.0.1
            


        
            org.projectlombok
            lombok
            1.18.12
        
        
        
            junit
            junit
            4.12
        
        
        
            mysql
            mysql-connector-java
            5.1.47
        
        
        
            com.mchange
            c3p0
            0.9.5.5
        
        
        
            javax.servlet
            servlet-api
            2.5
        
        
            javax.servlet.jsp
            jsp-api
            2.2
        
        
            javax.servlet
            jstl
            1.2
        
        
        
            org.mybatis
            mybatis
            3.5.2
        
        
            org.mybatis
            mybatis-spring
            2.0.2
        
        
        
            org.springframework
            spring-webmvc
            5.1.9.RELEASE
        
        
            org.springframework
            spring-jdbc
            5.1.9.RELEASE
        
        
        
            com.alibaba
            fastjson
            1.2.80
        
    

    
    
        
            
                src/main/java
                
                    **/*.properties
                    **/*.xml
                
                false
            
            
                src/main/resources
                
                    **/*.properties
                    **/*.xml
                
                false
            
        
    
        
            
                org.mybatis.generator
                mybatis-generator-maven-plugin
                1.3.7
                
                    
                    true
                    true