Spring MVC的方法返回值和参数传递

1. SpringMVC方法的返回值类型

3.1String类作为返回值

3.1.1Controller层

/**
 * 返回值类型为String时，一般用于返回视图名称
 * 1、当方法返回值为null时，默认将请求路径当做视图   forward:/jsp/index.jsp       如果说没有视图解析器，返回值为null携带数据只能用json
 * 2、当方法返回一个String的字符串时，当字符串为逻辑视图名时只返回视图，如果携带数据则使用request，session或者json
 * 3、当方法返回值加入forward时代表转发，如果写为redirect：xxxx代表重定向，不是返回视图了，但是不会这样做！！
 */
@RequestMapping("/condRequest")
public String secondRequest(HttpServletRequest request, HttpServletResponse response){
    request.setAttribute("user","张三");
    return "forward:/jsp/index.jsp";
}

3.1.2页面

3.2void作为返回值

3.2.1Controller层

/**
 * 如果方法写成了void就跟原来servlet含义是差不多 的
 * json
 */
@RequestMapping(value = "/firstRequest",produces = "text/json;charset=utf-8")
public void firstRequest(HttpServletRequest request, HttpServletResponse response, HttpSession session) throws IOException {
    Invoicing info=new Invoicing();
    info.setUserName("张三");
    info.setPassword("123");
    /**
     * json格式传递
     */
    response.setCharacterEncoding("UTF-8");
    String value= JSON.toJSONString(info);
    response.getWriter().write(value);
}

3.2.2页面

3.3ModelAndView作为返回值

3.3.1Controller层

/**
 * ModelAndView
 * @param request   请求对象
 * @param response  响应对象
 * @return    ModelAndView  model是用来传递数据用的，view是所需要跳转的页面
 */
@RequestMapping("/model")
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response){
    ModelAndView modelAndView=new ModelAndView();
    //携带给页面数据
    modelAndView.addObject("user","鸭头");
    //指定跳转页面(视图解析器配置前后缀)
    modelAndView.setViewName("index");
    return modelAndView;
}

3.3.2页面

3.4Object作为返回值类型

3.4.1Controller层

/**
 *Object
 * 1.当方法返回值为null时，默认将请求路径当作视图  jsp/objectRequest.jsp  如果没有视图解析器，如果返回值为null携带数据只能用json
 * 2.当方法返回值为String类型字符串时，就是视图的逻辑名称
 * 3.当返回对象或者集合数据时要使用json格式字符串，可选fashjson手动转换 ，也可以使用jackson自动转换
 */
@RequestMapping("/objectRequest")
@ResponseBody
public  Object objectRequest(){
    List<Invoicing> invoicingList=new ArrayList<>();
    Invoicing invoicing=new Invoicing();
    invoicing.setUid(1);
    invoicing.setUserName("aaa");
    invoicing.setPassword("123");
    invoicing.setRealName("张三");
    invoicingList.add(invoicing);
    return invoicingList;
}

3.4.2页面

2. Spring MVC的自动装配

4.1请求参数的自动类型转换

JSP页面创建表单

<form method="post" action="/formRequest">
    姓名：<input id="userName" name="userName" class="userName"/><span></span><br/>
    密码：<input id="password"name="password" class="password"/><br/>

    <input type="submit" class="submit"/>
</form>

/**
 * 接收零散参数：装配原则为传递参数名和方法接收参数名
 * 手动装配@RequestParam   name代表页面发送的参数名字 ，required代表参数是否必须传递  false
 * 代表不传递，默认为true defaultValue代表默认  model代表给页面传递的数据
 */

@RequestMapping(value = "/formRequest")
public String formRequest(String userName,String password){
    System.out.println(userName+"\t"+password);
    return "welcome";
}

注意点*:控制器Controller中的方法参数名称必须和表单元素的name属性值保持一致

4.2使用@RequestParam注解

@RequestParam的作用是，当表单元素与控制器方法的参数不匹配的情况下，使用@RequestParam注解声明参数名称。

@RequestParam 有三个属性：

（1）value：请求参数名（必须配置）

（2）required：是否必需，默认为 true，即 请求中必须包含该参数，如果

没有包含，将会抛出异常（可选配置）

（3）defaultValue：默认值，如果设置了该值，required 将自动设为 false，

无论你是否配置了required，配置了什么值，都是 false（可选配置)

/**
 * 接收零散参数：装配原则为传递参数名和方法接收参数名
 * 手动装配@RequestParam   name代表页面发送的参数名字 ，required代表参数是否必须传递  false
 * 代表不传递，默认为true defaultValue代表默认  model代表给页面传递的数据
 */

@RequestMapping(value = "/formRequest")
public String formRequest(@RequestParam(name="userName",required = false,defaultValue = "张三")String username,@RequestParam(name = "password",required = false,defaultValue = "123")String password){
    System.out.println(username+"\t"+password);
    return "welcome";
}

4.3请求参数自动装配为对象

/*
* 对象参数：传递的对象参数和对象中的属性名保持一致
* */
@RequestMapping("/invoivingObject")
public String invoivingObject(Invoicing invoicing){
    System.out.println(invoicing.getUserName());
    return "welcome";
}

4.4restful风格参数传递

在使用 RESTful 风格之前，我们如果想要增加一条商品数据通常是这样的:

但是使用了 RESTful 风格之后就会变成:

/**
 * get请求时，如果需要传递参数，那么则把不能使用以往的方式？name=xxx&age=yy,但是现在要遵循restful风格，例：xxx/ttt/ddd
 * 根据地址栏url匹配拿值  使用@PathVariable(name=地址栏中的参数映射)
 *
 */

@RequestMapping("/restfulRequest/{b}/{d}")
@ResponseBody
public String restfulRequest(@PathVariable(name = "b") String username, @PathVariable(name = "d")String password){
    System.out.println(username+"\t"+password);
    return "welcome";
}

4.5域属性对象传递参数

<form method="post" action="/invoivingObject">
    姓名：<input id="userName" name="userName" class="userName"/><span></span><br/>
    密码：<input id="password"name="password" class="password"/><br/>
    teacherName1<input id="t_name" class="t_name" name="teacher.t_name"/>
    <input type="submit" class="submit"/>
</form>

public class Invoicing {
    private  Integer uid;
    private  String userName;
    private  String password;
    private  String realName;
    private Teacher teacher;
    private List<Teacher> teachersList;
    public List<Teacher> getTeachersList() {
        return teachersList;
    }
    public void setTeachersList(List<Teacher> teachersList) {
        this.teachersList = teachersList;
    }
    public Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    public Integer getUid() {
        return uid;
    }
    public void setUid(Integer uid) {
        this.uid = uid;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getRealName() {
        return realName;
    }
    public void setRealName(String realName) {
        this.realName = realName;
    }
    @Override
    public String toString() {
        return "Invoicing{" +
                "uid=" + uid +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", realName='" + realName + '\'' +
                ", teacher=" + teacher +
                ", teachersList=" + teachersList +
                '}';
    }
}

 /*
* 域属性传递：传递参数为：域属性名.属性名
* */
@RequestMapping("/invoivingObject")
public String invoivingObject(Invoicing invoicing){
    System.out.println(invoicing.getUserName());
    return "welcome";
}

4.6域属性集合传递参数

<form method="post" action="/invoivingObject">
    姓名：<input id="userName" name="userName" class="userName"/><span></span><br/>
    密码：<input id="password"name="password" class="password"/><br/>
    teacherName2<input id="t_name" class="t_name" name="teachersList[0].t_name"/>
    teacherName3<input id="t_name1"  name="teachersList[1].t_name"/>

    <input type="submit" class="submit"/>
</form>

public class Invoicing {
    private  Integer uid;
    private  String userName;
    private  String password;
    private  String realName;
    private Teacher teacher;
    private List<Teacher> teachersList;
    public List<Teacher> getTeachersList() {
        return teachersList;
    }
    public void setTeachersList(List<Teacher> teachersList) {
        this.teachersList = teachersList;
    }
    public Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    public Integer getUid() {
        return uid;
    }
    public void setUid(Integer uid) {
        this.uid = uid;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getRealName() {
        return realName;
    }
    public void setRealName(String realName) {
        this.realName = realName;
    }
    @Override
    public String toString() {
        return "Invoicing{" +
                "uid=" + uid +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", realName='" + realName + '\'' +
                ", teacher=" + teacher +
                ", teachersList=" + teachersList +
                '}';
    }
}

/*
* 集合参数传递:集合名[下标].属性名
* */

@RequestMapping("/teacherInvoicing")
@ResponseBody
public String teacherInvoicing(Invoicing invoicing){
    System.out.println(invoicing.getTeachersList());
    return "welcome";
}