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使用注解开发SpringMVC

配置文件中常见BUG

一、地址数必须成偶
xsi:schemaLocation="http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context
      https://www.springframework.org/schema/context/spring-context.xsd
      http://www.springframework.org/schema/mvc
      https://www.springframework.org/schema/mvc/spring-mvc.xsd">
二、配置中避免中文注释,否则会500!!(字符集问题)

1.新建项目

2.导入jar包

3.编写web.xml,注册DispatcherServlet

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0">
<!-- 注册servlet--> <servlet> <servlet-name>SpringMVC</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><!-- 通过初始化参数指定SpringMVC配置文件的位置,进行关联--> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:springmvc-servlet.xml</param-value> </init-param><!-- 启动级别,数字越小,启动越早--> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>SpringMVC</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping></web-app>

4.编写springmvc配置文件

<!-- 自动扫描包,让指定包下注解生效--> <context:component-scan base-package="com.bao"></context:component-scan><!-- 让Spring MVC不处理静态资源 .css .js .html --> <mvc:default-servlet-handler/><!-- 处理器映射器HandlerMapping 处理器适配器HandlerAdapter 自动配置自动注入--> <mvc:annotation-driven/><!-- 视图解析器--> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver"><!-- 前缀--> <property name="prefix" value="/WEB-INF/jsp/"></property><!-- 后缀--> <property name="suffix" value=".jsp"></property> </bean>

5.创建对应的控制类 controller

@Controller//自动走视图解析器public class HelloController { @RequestMapping("/hello") //@ResponseBodt 不走视图解析器 public String hello(Model model){ //封装数据 model.addAttribute("msg","你好,SpringMVC"); return "hello"; //return "redirect:/index.jsp"; 视图重定向,默认为转发 }}

6.最后完善前端视图和controller之间的对应

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body>${msg}</body></html>


7.测试运行调试

使用springMVC必须配置的三大件:

处理器映射器   处理器适配器   视图解析器

控制器Colltroller  @Colltroller

@Colltroller //走视图解析器
@RestColltroller //返回字符串

控制器负责解析用户的请求并将其转换为一个模型。
在Spring MVC中一个控制器类可以包含多个方法

@RequestMapping("/hello") //映射地址

    @RequestMapping("/chen")
  public String test1(@RequestParam("name") String name, Model model)
   
  加上 @RequestParam 会更直观的看到这是从前端所获取的参数

JSON(数据交换格式)

前后端分离时代:

后端部署后端,提供接口,提供数据;

前端独立部署,负责渲染后端的数据;

<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.9.8</version> </dependency>  @RequestMapping("/j1") @ResponseBody //不走视图解析器 public String json1() throws JsonProcessingException { ObjectMapper mapper = new ObjectMapper(); List<User> userList = new ArrayList<User>();
User user1 = new User(50,"陈1",3); User user2 = new User(49,"陈2",3); User user3 = new User(51,"陈3",3); userList.add(user1); userList.add(user2); userList.add(user3);
String s = mapper.writeValueAsString(userList); return s; }


JSON乱码问题

<mvc:annotation-driven> <!--解决json乱码问题--> <mvc:message-converters register-defaults="true"> <bean class="org.springframework.http.converter.StringHttpMessageConverter"> <constructor-arg value="UTF-8"/> </bean> <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"> <property name="objectMapper"> <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"> <property name="failOnEmptyBeans" value="false"/> </bean> </property> </bean> </mvc:message-converters></mvc:annotation-driven>

FastJson

fastjson.jar是阿里开发的一款专门用于Java开发的包,可以方便实现json对象与JavaBean对象的转换

FastJson需要的jar包、测试

<dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.75</version></dependency>
@RequestMapping("/j2") @ResponseBody //不走视图解析器 public String json2() throws JsonProcessingException {
List<User> userList = new ArrayList<User>(); User user1 = new User(50,"陈1",3); User user2 = new User(49,"陈2",3); User user3 = new User(51,"陈3",3); userList.add(user1); userList.add(user2); userList.add(user3);
String s = JSON.toJSONString(userList); return s; }