13、spring mvc用@ResponseBody实现jso

今天踩的坑，记录一下。本来前端使用ajax只传了一个参数给后台，没有拼json串，后台从request中取的值。后来想要多传一个参数，那不如直接传个对象，手动转json串很low，既然spring mvc可以帮我们做，那就用它的。
只传一个参数前后端代码如下：

function verifyRepeateName() {
    var nameVal = $('#name').val();
    var requestUrl = '[[@{/}]]' + 'testSuite/verifyRepeateName';
    $.ajax({type:'post', url:requestUrl, async:true, data:{name:nameVal}, success:function(result){
        console.log('result:' + result);
        if(result != '') {
            $('#errorMsg').text(result);
        }
    }});
}

@RequestMapping(value = "/verifyRepeateName", method = RequestMethod.POST)
@ResponseBody
public String verifyRepeateName(HttpServletRequest request) {
    String name = request.getParameter("name");
    if(!StringUtils.isEmpty(name)) {
        boolean repeatedFlag = testSuiteService.verifyRepeateName(name);
        if(repeatedFlag) {
            return ResponseConstant.REPEATEDNAMEVALUE;
        } else {
            return "";
        }
    } else {
        return "";
    }
}

传json串的方法如下：
1、spring mvc 用jaskson做json和对象互相转换，故引入

<!--spring mvc jackson-->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.8.7</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.8.7</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.8.7</version>
</dependency>

2、发请求时指定数据类型为json

dataType:"json",
contentType:"application/json",

不加这两个报415

3、传的json是手动拼的，格式不对，报415，可是格式改了之后报400，这样根本不知道是哪里错误了，找到了一个在后台打印错误的方法。参考http://www.jb51.net/article/120350.htm

@ResponseBody
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(HttpMessageNotReadableException.class)
public String messageNotReadable(HttpMessageNotReadableException exception,
 HttpServletResponse response){
    logger.error("请求参数不匹配。", exception);
    return exception.getMessage();
}

后台有打印错误了：
[2018-02-01 15:46:54,708] [http-nio-7280-exec-10] [ERROR] com.picc.autoplateform.controller.TestSuiteController 请求参数不匹配。
org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Can not construct instance of com.picc.autoplateform.model.TestSuite: no String-argument constructor/factory method to deserialize from String value ('{"testsuiteid":"7f429842-2c99-4f13-8208-852e8881a23c", "memo":"test", "runenv":"", "runtime":"", "projectid":"", "browsertype":"","userid":"", "createtime":"", "validflag":"", "name":"", "runtype":""}');
大致意思就是无法解析json串咯，不知道为什么，此时json格式是正确的。
于是手动建一个对象，再转成json串，竟然可以了。

4、前后台代码如下

function verifyRepeateName() {
    var obj = {};
    obj.testsuiteid = '[[${TESTSUITEEDIT.testsuiteid}]]';
    obj.name = $('#name').val();
    console.log('obj:' + obj);
    console.log('JSON.stringify(obj):' + JSON.stringify(obj));
    var requestUrl = '[[@{/}]]' + 'testSuite/verifyRepeateName';
    var resultMsg = '';
    $.ajax({type:'post',
        url:requestUrl,
        async:false,
        dataType:"json",
        contentType:"application/json",
        data:JSON.stringify(obj),
        success:function(result){
            console.log('success result:' + result);
            $('#errorMsg').text(result.responseMsg);
        }, error: function(result) {
            console.log('error result:' + result);
        }
    });
}

@RequestMapping(value = "/verifyRepeateName", method = RequestMethod.POST)
@ResponseBody
public String verifyRepeateName(@RequestBody TestSuite testSuite) {
    String name = testSuite.getName();
    String testSuiteId = testSuite.getTestsuiteid();
    if(!StringUtils.isEmpty(name)) {
        boolean repeatedFlag = testSuiteService.verifyRepeateName(name, testSuiteId);
        if(repeatedFlag) {
            return "{\"responseMsg\":\"" + ResponseConstant.REPEATEDNAMEVALUE + "\"}";
        } else {
            return "{\"responseMsg\":\"" + ResponseConstant.NOREPEATE + "\"}";
        }
    } else {
        return "{\"responseMsg\":\"" + ResponseConstant.NOREPEATE + "\"}";
    }
}

5、注意：指定了dataType:"json",contentType:"application/json",这两项，返回数据的格式必须是json了，之前返回的是一个提示信息，报错。