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A response to the data
1.1 returns a string
- Controller method returns the string to specify the name of the logical view, a view resolver address to a physical view.
Example: In the index.jsp click on the link to jump to the page success.jsp
/*********************index.jsp**********************/
<a href="test/testReturnString">testReturnString</a>
/****************TestResponse.java*******************/
@Controller
@RequestMapping("/test")
public class TestResponse {
//指定逻辑视图名，经过视图解析器解析为 jsp 物理路径：/WEB-INF/pages/success.jsp
@RequestMapping("/testReturnString")
public String testReturnString(){
System.out.println("testReturnString方法执行了");
return "success";
}
}
operation result:
1.2 void return type
- If the controller method returns the value written to void, reported abnormal execution program 404, the default look JSP page not found. The default will jump to @RequestMapping (value = "/ XXX") XXX page.
/*********************index.jsp**********************/
<a href="/test/testVoid">testVoid</a><br/>
/****************TestResponse.java*******************/
@RequestMapping("/testVoid")
public void testVoid(){
System.out.println("testVoid方法执行了");
}
The result:
it may be the original Servlet API methods as parameters of the controller, used to forward or redirect the request to jump to a specific page.
@RequestMapping("/testvoid")
public void testvoid(HttpServletRequest request, HttpServletResponse response) throws Exception{
// 设置中文乱码
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
//第一种：请求转发
request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);
//第二种：重定向
response.sendRedirect("testReturnString");
//第三种：直接响应
response.getWriter().print("testAdd执行了");
}
1.3 return type is ModelAndView
- Spring ModelAndView object is the providing of the object can be used as the return value of the controller, can be used to adjust the specific JSP view.
/*********************index.jsp**********************/
<a href="test/testModelAndView">testModelAndView</a><br/>
/****************TestResponse.java*******************/
@RequestMapping("/testModelAndView")
public ModelAndView testModelAndView() throws Exception{
ModelAndView mv = new ModelAndView();
User user = new User();
user.setUname("叶子");
user.setAge(21);
// 把user对象存储到mv对象中，也会把user对象存入到request对象
mv.addObject(user);
// 用于设置逻辑视图名称，视图解析器会根据名称前往指定的视图
mv.setViewName("success");
return mv;
}
/****************success.jsp*******************/
对象：${user}<br/>
姓名：${user.uname}
operation result:
1.4 json response data
- SpringMVC can be used in response to json @ResponseBody annotation data, the annotation Controller object methods returned by HttpMessageConverter interface into the specified format of the data, in response to the response by the client
Springmvc default data converted to json MappingJacksonHttpMessageConverter, need to be added jackson package.
<!---------------pom.xml--------------->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.9.0</version>
</dependency>
/*********************index.jsp**********************/
<script>
// 页面加载，绑定单击事件
$(function () {
$("#btn").click(function () {
$.ajax({
url:"test/testAjax",
type:"post",
dataType:"json",
contentType:"application/json;charset=UTF-8",
data:'{"uname":"叶子","age":21}',
success:function (data) {
alert(data+"---"+data.uname);
}
})
})
})
</script>
/****************TestResponse.java*******************/
@RequestMapping("/testAjax")
public @ResponseBody User testAjax(@RequestBody User user){
System.out.println(user);
return user;
}
operation result:
1.5 Forwarding and Redirection
- controller 方法在提供了 String 类型的返回值之后，默认就是请求转发。
转发：
“forward:url” ，不走视图解析器了，所以需要编写完整的路径 ，它相当于request.getRequestDispatcher(“url”).forward(request,response)，使用请求转发，既可以转发到 jsp，也可以转发到其他的控制器方法。
重定向：
“redirect:url” ，它相当于“response.sendRedirect(url)”。
需要注意的是，如果是重定向到 jsp 页面，则 jsp 页面不 能写在 WEB-INF 目录中，否则无法找到。
/*********************index.jsp**********************/
<a href="test/testForwardOrRedirect">testForwardOrRedirect</a>
/****************TestResponse.java*******************/
@RequestMapping("/testForwardOrRedirect")
public String testForwardOrRedirect(){
// 请求转发
return "forward:/WEB-INF/pages/success.jsp";
// 重定向
return "redirect:testModelAndView";
}
二、异常处理
- 系统中异常包括两类：预期异常和运行时异常 RuntimeException，前者通过捕获异常从而获取异常信息， 后者主要通过规范代码开发、测试通过手段减少运行时异常的发生。
- 系统的 dao、service、controller 出现都通过 throws Exception 向上抛出，最后由 springmvc 前端 控制器交由异常处理器进行异常处理，如下图：
-
2.1 使用HandlerExceptionResolver接口
创建一个自定义异常类CustomException
public class CustomException extends Exception {
private String message;
public CustomException(String message){
this.message = message;
}
public String getMessage() {
return message;
}
}
在exception 包中创建一个 HandlerExceptionResolver 接口的实现类 CustomExceptionResoler ，具体代码如下：
public class CustomExceptionResoler implements HandlerExceptionResolver {
@Override
public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
ex.printStackTrace();
CustomException ce = null;
//如果抛出的是系统自定义异常则直接转换
if(ex instanceof CustomException){
ce = (CustomException) ex;
}else {
//如果抛出的不是系统自定义异常则重新构造一个系统错误异常。
ce = new CustomException("系统错误，请与系统管理员联系");
}
ModelAndView modelAndView = new ModelAndView();
modelAndView.addObject("message",ce.getMessage());
modelAndView.setViewName("error");
return modelAndView;
}
}
需要将实现类 CustomExceptionResoler 在配置文件中托管给 Spring MVC 框架才能进行异常的统一处理，配置代码为 ：
<bean id="handlerExceptionResolver"
class="com.wink.exception.CustomExceptionResoler"/>
When using SimpleMappingExceptionResolver class unified handling exceptions, you need to configure the corresponding relationship between abnormal and View class in advance in the configuration file. springmvc.xml:
<!--SimpleMappingExceptionResolver（异常类与 View 的对应关系） -->
<bean
class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<!-- 定义默认的异常处理页面，当该异常类型注册时使用 -->
<property name="defaultErrorView" value="error"></property>
<!-- 定义异常处理页面用来获取异常信息的变量名，默认名为exception -->
<property name="exceptionAttribute" value="ex"></property>
<!-- 定义需要特殊处理的异常，用类名或完全路径名作为key，异常页名作为值 -->
<property name="exceptionMappings">
<props>
//如：<prop key="java.sql.SQLException">sql-error</prop>
<!-- 在这里还可以继续扩展对不同异常类型的处理 -->
</props>
</property>
</bean>
In a statement annotation using @ExceptionHandler unified treatment not need to configure anything abnormal.
Creating BaseController class and use @ExceptionHandler notes the statement in the class exception handling:
public class BaseController {
@ExceptionHandler
public String exception(HttpServletRequest request, Exception ex) {
request.setAttribute("ex", ex);
// 根据不同错误转向不同页面
......
}
}
All Controller needs exception handling inherit BaseController categories:
@Controller
public class TestException extends BaseController{
......
}
