Spring MVC 前后台传值情况汇总

一、前台通过$.ajax的GET请求传值

1.前端参数写在url中：
前台代码：

$.ajax({
            type: 'GET',
            url: '/user/login?username=admin&password=admin',
            dataType: 'JSON',
            success: function (res) {
                $('#result').text(res);
            },
            error: function () {
                $('#result').text('error!');
            }
        });

后台代码：

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

    private static final Logger LOG = LoggerFactory.getLogger(UserController.class);

    @Autowired
    private UserService userService;

    @RequestMapping(value = "/login", method = {RequestMethod.GET})
    @ResponseBody
    public boolean login(UserForm userForm) {
        LOG.info("username: " + userForm.getUsername() + ";password: " + userForm.getPassword());
        Map<String, String> param = new HashMap<String, String>();
        param.put("username", userForm.getUsername());
        param.put("password", userForm.getPassword());
        return userService.checkUserExists(param);
    }
}

2.前台data参数使用$.param()函数对JS对象进行转化

$.ajax({
            type: 'GET',
            url: '/user/login',
            dataType: 'JSON',
            data: $.param({
                username: 'admin',
                password: 'admin'
            }),
            success: function (res) {
                $('#result').text(res);
            },
            error: function () {
                $('#result').text('error!');
            }
        });

后台同上，不过也可以使用如下

@RequestMapping(value = "/login", method = {RequestMethod.GET})
    @ResponseBody
    public boolean login(String username, String password) {
        LOG.info("username: " + username + ";password: " + password);
        Map<String, String> param = new HashMap<String, String>();
        param.put("username", username);
        param.put("password", password);
        return userService.checkUserExists(param);
    }

1. 前台data参数直接传JS对象

$.ajax({
            type: 'GET',
            url: '/user/login',
            dataType: 'JSON',
            data: {
                username: 'admin',
                password: 'admin'
            },
            success: function (res) {
                $('#result').text(res);
            },
            error: function () {
                $('#result').text('error!');
            }
        });

后台同上，不过也可以使用如下：

@RequestMapping(value = "/login", method = {RequestMethod.GET})
    @ResponseBody
    public boolean login(@RequestParam("username") String name, @RequestParam("password") String pass) {
        LOG.info("username: " + name + ";password: " + pass);
        Map<String, String> param = new HashMap<String, String>();
        param.put("username", name);
        param.put("password", pass);
        return userService.checkUserExists(param);
    }

注意：经验证$.ajax使用GET请求时
1.前台data参数不能为JSON串，否则后台无法接收，报415错误;
2.后台如果使用封装的Entity接收参数，不可以加@RequestBody注解，否则接收的参数都为NULL;

一、前台通过$.ajax的POST请求传值

1. 前台使用JS对象时
   前端代码：

$.ajax({
            type: 'POST',
            url: '/user/login',
            dataType: 'JSON',
            data: {
                username: 'admin',
                password: 'admin'
            },
            success: function (res) {
                $('#result').text(res);
            },
            error: function () {
                $('#result').text('error!');
            }
        });

后端同一中的三种接收方式。
至此已经感觉够用了，但是考虑后端接收参数能否直接使用Map接收，那么可不必再转化为Map即可调用后台的mybatis，这就用到了用到了@RequestBody
2. 修改前台代码，后台用@RequestBody 转为Map接收
前台代码：

$.ajax({
            type: 'POST',
            url: '/user/login',
            contentType: 'application/json',
            dataType: 'JSON',
            data: JSON.stringify({
                username: 'admin',
                password: 'admin'
            }),
            success: function (res) {
                $('#result').text(res);
            },
            error: function () {
                $('#result').text('error!');
            }
        });

后台代码：

@RequestMapping(value = "/login", method = {RequestMethod.POST})
    @ResponseBody
    public boolean login(@RequestBody Map<String, String> param) {
        return userService.checkUserExists(param);
    }

当然也可以这样了：

@RequestMapping(value = "/login", method = {RequestMethod.POST})
    @ResponseBody
    public boolean login(@RequestBody UserForm userForm) {
        LOG.info("username: " + userForm.getUsername() + ";password: " + userForm.getPassword());
        Map<String, String> param = new HashMap<String, String>();
        param.put("username", userForm.getUsername());
        param.put("password", userForm.getPassword());
        return userService.checkUserExists(param);
    }

---

目前想到的就是这么多的方式，尤其要注意$.ajax的POST请求时，如果后台使用@RequestBody接收，前台需要添加contentType: ‘application/json’，并且data要发送的是JSON串，JS对象会报错误