Spring MVC 实践
标签 ： Java与Web
Spring Web MVC
Spring-Web-MVC是一种基于请求驱动的 轻量级Web-MVC设计模式框架, Spring MVC使用MVC架构思想, 对Web层进行职责解耦 ,使用请求-响应 模型将数据 、业务 与视图 进行分离, 简化开发.
MVC
MVC(模型-视图-控制器)是一个以设计界面应用程序为基础 的架构模式,通过分离模型-视图-控制器在应用中的角色将业务逻辑从界面中解耦:
模型负责封装应用数据和业务逻辑; 视图仅负责展示数据; 控制器负责接收用户请求,并调用模型(Service/Manger/DAO)来处理业务逻辑.模型可能会返回一些数据需要在视图层展示,控制器就需要整理模型数据并调用视图展示. MVC模式的核心思想就是将业务逻辑从界面中分离出来,允许它们单独改变而不会相互影响.
Spring MVC
Spring MVC框架是基于Java语言的MVC架构具体实现.他的设计围绕DispatcherServlet展开,DispatcherServlet负责将请求分派给指定的Controller(Handler),通过可配置的HandlerMapping、HandlAdapter、Controller、ViewResolver来处理请求 拿到数据并填充对应的视图View :
组件名称描述 DispatcherServlet 调度器/前端控制器 DispatcherServlet是前端控制器 模式的具体实现(详细可参考Front Controller),他提供了整个Web应用的集中访问点,截获请求并将其分派给指定的Controller,相当于MVC中的C. 他的存在降低了组件之间的耦合性. HandlerMapping 处理器映射器 HandlerMapping负责根据用户请求URI找到对应的Controller与Interceptor,并将它们封装在HandlerExecutionChain中返回给DispatcherServlet. HandlAdapter 处理器适配器 Spring MVC通过HandlerAdapter执行Controller,这是适配器模式 的应用,通过扩展适配器可以执行更多类型的Controller. Controller 处理器 Controller(又称Handler)是继DispatcherServlet前端控制器之后的后端控制器 ,在DispatcherServlet的控制下Controller对具体的用户请求进行处理. ViewResolver 视图解析器 负责将Model数据填充到View, 组合生成视图展示:他首先将逻辑视图名 解析成物理视图名 ,生成View视图对象,最后对View进行渲染(填充数据). Spring默认提供了针对JSP/Velocity/PFD等视图的ViewResolver实现.
初识Spring MVC
需求: 用户列表查询.
mvn archetype:generate -DgroupId=com.fq.mvc -
DartifactId =MVC
-
DarchetypeArtifactId =maven-archetype-webapp
-
DinteractiveMode =false
-
DarchetypeCatalog =internal依赖管理 Spring 、Spring MVC 、 Sevlet 及Velocity 依赖: <dependency > <groupId > org.springframework
</groupId > <artifactId > spring-core
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-context
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-context-support
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-beans
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-expression
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-web
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-test
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > javax.servlet
</groupId > <artifactId > javax.servlet-api
</artifactId > <version > ${servlet.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-webmvc
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.apache.velocity
</groupId > <artifactId > velocity
</artifactId > <version > ${velocity.version}
</version >
</dependency >
<dependency > <groupId > org.apache.velocity
</groupId > <artifactId > velocity-tools
</artifactId > <version > ${velocity.tools.version}
</version >
</dependency >
配置DispatcherServlet(web.xml) <?xml version="1.0" encoding="UTF-8"?>
<web-app version ="3.0" xmlns ="http://java.sun.com/xml/ns/javaee" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" > <display-name > MVC
</display-name > <servlet > <servlet-name > mvc
</servlet-name > <servlet-class > org.springframework.web.servlet.DispatcherServlet
</servlet-class > <init-param > <param-name > contextConfigLocation
</param-name > <param-value > classpath:spring/mvc-servlet.xml
</param-value > </init-param > <load-on-startup > 1
</load-on-startup > </servlet > <servlet-mapping > <servlet-name > mvc
</servlet-name > <url-pattern > *.do
</url-pattern > </servlet-mapping >
</web-app >
配置HandlerMapping/HandlerAdapter(mvc-servlet.xml) <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns ="http://www.springframework.org/schema/beans" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd" > <bean class ="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping" /> <bean class ="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter" />
</beans >
/*** @author jifang* @since 16/3/15 下午4:40.*/
public class UserController implements Controller {@Override public ModelAndView
handleRequest (HttpServletRequest request, HttpServletResponse response)
throws Exception {List<User> users =
new ArrayList<>();users.add(
new User(
1 ,
"翡青" ,
new Date(),
1 ,
"浙江-杭州" ));users.add(
new User(
2 ,
"小芳" ,
new Date(),
2 ,
"山东-青岛" ));ModelAndView result =
new ModelAndView();result.addObject(
"users" , users);result.setViewName(
"users" );
return result;}
}
<bean name ="/mvc/users.do" class ="com.fq.mvc.controller.UserController" />
配置ViewResolver(mvc-servlet.xml) Velocity ,因此配置VelocityViewResolver: <bean id ="viewResolver" class ="org.springframework.web.servlet.view.velocity.VelocityViewResolver" > <property name ="suffix" value =".vm" /> <property name ="contentType" value ="text/html;charset=UTF-8" /> <property name ="dateToolAttribute" value ="dateTool" /> <property name ="numberToolAttribute" value ="numberTool" /> <property name ="exposeRequestAttributes" value ="false" /> <property name ="exposeSessionAttributes" value ="true" />
</bean >
<bean id ="velocityConfigurer" class ="org.springframework.web.servlet.view.velocity.VelocityConfigurer" > <property name ="resourceLoaderPath" value ="views" /> <property name ="velocityProperties" > <props > <prop key ="input.encoding" > UTF-8
</prop > <prop key ="output.encoding" > UTF-8
</prop > </props > </property >
</bean >
<html >
<head > <title > 用户列表
</title > <link rel ="stylesheet" href ="/css/main.css" > <meta http-equiv ="content-type" content ="text/html; charset=UTF-8" />
</head >
<body >
<div id ="global" > <fieldset > <legend > 用户列表:
</legend > <table width ="100%" border =0 > <tr > <td > ID
</td > <td > username
</td > <td > birthday
</td > <td > sex
</td > <td > address
</td > </tr > #foreach($user in $users)
<tr > <td > ${user.id}
</td > <td > ${user.name}
</td > <td > ${user.birthday}
</td > #if(${user.sex} == 1)
<td > 男
</td > #else
<td > 女
</td > #end
<td > ${user.address}
</td > </tr > #end
</table > </fieldset >
</div >
</body >
</html >
参考: main.css地址:OSChina
小结
前端控制器
*.do: 拦截所有以.do结尾的URI. / : 拦截 所有 URI. 处理器映射器
处理器适配器
视图解析器 Velocity 作为视图展示,如果使用的是JSP的话, 需要配置另一种视图解析器InternalResourceViewResolver:
<bean class ="org.springframework.web.servlet.view.InternalResourceViewResolver" > <property name ="viewClass" value ="org.springframework.web.servlet.view.JstlView" /> <property name ="prefix" value ="/views" /> <property name ="suffix" value =".jsp" />
</bean >
注解初步
从2.5版本开始, Spring引入了注解开发:
注解驱动(mvc-servlet.xml) 从3.1版本开始,Spring MVC使用RequestMappingHandlerMapping 注解式处理器映射器 对标有@ResquestMapping的方法进行映射 . 从3.1版本开始,Spring MVC使用RequestMappingHandlerAdapter 注解式处理器适配器 对标记有@ResquestMapping的方法进行适配 . Spring MVC使用<mvc:annotation-driven/> 注解驱动 自动加载RequestMappingHandlerMapping和RequestMappingHandlerAdapter及其他相关配置. 因此在mvc-servlet.xml最简单有效的配置方式是使用<mvc:annotation-driven/>替代注解处理器和适配器: <mvc:annotation-driven />
尽管<mvc:annotation-driven/>很小, 但他具有足够的威力, 它注册了很多的特性, 包括对JSR-303校验、信息转换以及对域格式化的支持.
组件扫描(mvc-servlet.xml):
<
context :
component -scan base-
package =
"com.fq.mvc.controller" />
@Controller
@RequestMapping (
"/mvc" )
public class UserController {@RequestMapping (
"/users.do" )
public ModelAndView
users () {List<User> users =
new ArrayList<>();users.add(
new User(
1 ,
"翡青" ,
new Date(),
1 ,
"浙江-杭州" ));users.add(
new User(
2 ,
"小芳" ,
new Date(),
2 ,
"山东-青岛" ));ModelAndView result =
new ModelAndView();result.addObject(
"users" , users);result.setViewName(
"users" );
return result;}
}
使用基于注解的`Controller`有以下优点:- 基于注解的`Controller`请求映射关系不存储在配置文件中,使用`@RequestMappeing`便可以对一个方法进行映射.- 一个`Controller`内可以有多个处理方法,可以响应多个动作,这样就允许将同一模块的多个操作写在同一个`Controller`里面,便于模块划分,且减少类的数量.
集成MyBatis
通过Spring将各层整合: 持久层DAO(MyBatis的Mapper)注册到Spring容器中. 业务层Service/Manager从Spring容器中拿到DAO接口, 并注册Service服务. 表现层Controller从Spring容器中拿到Service接口, 通过Spring MVC进行数据展示.
需求: 展示所有用户数据(由于数据模型较简单, 因此从DAO到Controller只使用一个DO对象-User).
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-core
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-context
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-context-support
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-beans
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-expression
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-web
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-test
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-aop
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-aspects
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > javax.servlet
</groupId > <artifactId > javax.servlet-api
</artifactId > <version > ${servlet.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-webmvc
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.apache.velocity
</groupId > <artifactId > velocity
</artifactId > <version > ${velocity.version}
</version >
</dependency >
<dependency > <groupId > org.apache.velocity
</groupId > <artifactId > velocity-tools
</artifactId > <version > ${velocity.tools.version}
</version >
</dependency >
<dependency > <groupId > org.mybatis
</groupId > <artifactId > mybatis
</artifactId > <version > 3.3.0
</version >
</dependency >
<dependency > <groupId > mysql
</groupId > <artifactId > mysql-connector-java
</artifactId > <version > ${mysql.version}
</version >
</dependency >
<dependency > <groupId > com.zaxxer
</groupId > <artifactId > HikariCP
</artifactId > <version > ${hikaricp.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-jdbc
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.springframework
</groupId > <artifactId > spring-tx
</artifactId > <version > ${spring.version}
</version >
</dependency >
<dependency > <groupId > org.mybatis
</groupId > <artifactId > mybatis-spring
</artifactId > <version > ${mybatis.spring.version}
</version >
</dependency >
<dependency > <groupId > ch.qos.logback
</groupId > <artifactId > logback-classic
</artifactId > <version > ${logback.version}
</version >
</dependency >
集成MyBatis
mybatis-configuration.xml <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration > <mappers > <mapper resource ="mybatis/mapper/UserDAO.xml" /> </mappers >
</configuration >
/*** @author jifang.* @since 2016/5/26 11:16.*/
public class User {private int id;
private String name;
private Date birthday;
private int sex;
private String address;
public User () {}
public User (
int id, String name, Date birthday,
int sex, String address) {
this .id = id;
this .name = name;
this .birthday = birthday;
this .sex = sex;
this .address = address;}
public int getId () {
return id;}
public void setId (
int id) {
this .id = id;}
public String
getName () {
return name;}
public void setName (String name) {
this .name = name;}
public Date
getBirthday () {
return birthday;}
public void setBirthday (Date birthday) {
this .birthday = birthday;}
public int getSex () {
return sex;}
public void setSex (
int sex) {
this .sex = sex;}
public String
getAddress () {
return address;}
public void setAddress (String address) {
this .address = address;}
}
/*** @author jifang* @since 16/3/20 下午5:47.*/
public interface UserDAO {List<User> selectAllUsers();
}
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace ="com.fq.mvc.dao.UserDAO" > <select id ="selectAllUsers" resultType ="com.fq.mvc.domain.User" > SELECT *FROM user;
</select > </mapper >
applicationContext-datasource.xml(配置数据源) <beans xmlns ="http://www.springframework.org/schema/beans" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xmlns:context ="http://www.springframework.org/schema/context" xsi:schemaLocation ="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd" > <context:property-placeholder location ="classpath:db.properties" /> <bean id ="hikariConfig" class ="com.zaxxer.hikari.HikariConfig" > <property name ="driverClassName" value ="${mysql.driver.class}" /> <property name ="jdbcUrl" value ="${mysql.url}" /> <property name ="username" value ="${mysql.user}" /> <property name ="password" value ="${mysql.password}" /> <property name ="maximumPoolSize" value ="5" /> <property name ="maxLifetime" value ="700000" /> <property name ="idleTimeout" value ="600000" /> <property name ="connectionTimeout" value ="10000" /> <property name ="dataSourceProperties" > <props > <prop key ="dataSourceClassName" > com.mysql.jdbc.jdbc2.optional.MysqlDataSource
</prop > <prop key ="cachePrepStmts" > true
</prop > <prop key ="prepStmtCacheSize" > 250
</prop > <prop key ="prepStmtCacheSqlLimit" > 2048
</prop > </props > </property > </bean > <bean id ="dataSource" class ="com.zaxxer.hikari.HikariDataSource" destroy-method ="close" > <constructor-arg ref ="hikariConfig" /> </bean > <bean id ="sqlSessionFactory" class ="org.mybatis.spring.SqlSessionFactoryBean" > <property name ="dataSource" ref ="dataSource" /> <property name ="configLocation" value ="classpath:mybatis/mybatis-configuration.xml" /> </bean > <bean class ="org.mybatis.spring.mapper.MapperScannerConfigurer" > <property name ="basePackage" value ="com.fq.mvc.dao" /> <property name ="sqlSessionFactoryBeanName" value ="sqlSessionFactory" /> </bean > <bean id ="transactionManager" class ="org.springframework.jdbc.datasource.DataSourceTransactionManager" > <property name ="dataSource" ref ="dataSource" /> </bean > </beans >
## Data Source
mysql
.driver .class =
com .mysql .jdbc .Driver
mysql
.url =jdbc:mysql://host:port/db?characterEncoding=utf-
8
mysql
.user =user
mysql
.password =password
集成Service
public interface UserService {List<User> getAllUsers();
}
@Service
public class UserServiceImpl implements UserService {@Autowired private UserDAO dao;
@Override public List<User>
getAllUsers () {
return dao.selectAllUsers();}
}
applicationContext.xml(配置组件扫描与事务控制) <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns ="http://www.springframework.org/schema/beans" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xmlns:context ="http://www.springframework.org/schema/context" xmlns:tx ="http://www.springframework.org/schema/tx" xmlns:aop ="http://www.springframework.org/schema/aop" xsi:schemaLocation ="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/txhttp://www.springframework.org/schema/tx/spring-tx.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd" > <import resource ="applicationContext-datasource.xml" /> <context:component-scan base-package ="com.fq.mvc.service" /> <bean id ="transactionManager" class ="org.springframework.jdbc.datasource.DataSourceTransactionManager" > <property name ="dataSource" ref ="dataSource" /> </bean > <tx:advice id ="txAdvice" transaction-manager ="transactionManager" > <tx:attributes > <tx:method name ="select*" timeout ="-1" propagation ="REQUIRED" read-only ="true" /> </tx:attributes > </tx:advice > <aop:config > <aop:advisor advice-ref ="txAdvice" pointcut ="execution(* com.fq.mvc.service.impl.UserServiceImpl.*(..))" /> </aop:config > </beans >
集成MVC
@Controller
@RequestMapping (
"/mvc" )
public class UserController {@Autowired private UserService service;
@RequestMapping (value =
"/user.do" )
public ModelAndView
users () {List<User> users = service.getAllUsers();
return new ModelAndView(
"users" ,
"users" , users);}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns ="http://www.springframework.org/schema/beans" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc ="http://www.springframework.org/schema/mvc" xmlns:context ="http://www.springframework.org/schema/context" xsi:schemaLocation ="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/mvchttp://www.springframework.org/schema/mvc/spring-mvc.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd" > <mvc:annotation-driven /> <context:component-scan base-package ="com.fq.mvc.controller" /> <bean id ="viewResolver" class ="org.springframework.web.servlet.view.velocity.VelocityViewResolver" > <property name ="suffix" value =".vm" /> <property name ="contentType" value ="text/html;charset=UTF-8" /> <property name ="dateToolAttribute" value ="dateTool" /> <property name ="numberToolAttribute" value ="numberTool" /> <property name ="exposeRequestAttributes" value ="false" /> <property name ="exposeSessionAttributes" value ="true" /> </bean > <bean id ="velocityConfigurer" class ="org.springframework.web.servlet.view.velocity.VelocityConfigurer" > <property name ="resourceLoaderPath" value ="views" /> <property name ="velocityProperties" > <props > <prop key ="input.encoding" > UTF-8
</prop > <prop key ="output.encoding" > UTF-8
</prop > </props > </property > </bean >
</beans >
<?xml version="1.0" encoding="UTF-8"?>
<web-app version ="3.0" xmlns ="http://java.sun.com/xml/ns/javaee" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" > <display-name > MVC
</display-name > <listener > <listener-class > org.springframework.web.context.ContextLoaderListener
</listener-class > </listener > <context-param > <param-name > contextConfigLocation
</param-name > <param-value > classpath:spring/applicationContext.xml
</param-value > </context-param > <servlet > <servlet-name > mvc
</servlet-name > <servlet-class > org.springframework.web.servlet.DispatcherServlet
</servlet-class > <init-param > <param-name > contextConfigLocation
</param-name > <param-value > classpath:spring/mvc-servlet.xml
</param-value > </init-param > <load-on-startup > 1
</load-on-startup > </servlet > <servlet-mapping > <servlet-name > mvc
</servlet-name > <url-pattern > *.do
</url-pattern > </servlet-mapping >
</web-app >
集成log
为了能够看到Spring MVC的运行时信息 , 最好在应用中集成一种Log实现, 在此选用LogBack :
<configuration > <property name ="log_root_dir" value ="/data/logs/mvc/" /> <property name ="log_pattern" value ="%d{HH:mm:ss.SSS} [%thread] %-5level %logger{0} - %msg%n" /> <appender name ="STD_OUT" class ="ch.qos.logback.core.ConsoleAppender" > <encoder > <pattern > ${log_pattern}
</pattern > </encoder > </appender > <appender name ="FILE_OUT" class ="ch.qos.logback.core.rolling.RollingFileAppender" > <rollingPolicy class ="ch.qos.logback.core.rolling.TimeBasedRollingPolicy" > <fileNamePattern > ${log_root_dir}/mvc-server.%d{YY-MM-dd}.log
</fileNamePattern > <maxHistory > 7
</maxHistory > </rollingPolicy > <encoder > <pattern > ${log_pattern}
</pattern > </encoder > </appender > <root level ="DEBUG" > <appender-ref ref ="STD_OUT" /> <appender-ref ref ="FILE_OUT" /> </root > </configuration >
注解开发
需求: 实现User添加.
<html >
<head > <title > 用户添加
</title > <link rel ="stylesheet" href ="/css/main.css" > <meta http-equiv ="content-type" content ="text/html; charset=UTF-8" />
</head >
<body >
<div id ="global" > <fieldset > <legend > Add a User
</legend > <form action ="/mvc/add_user.do" method ="post" > <p > <label for ="name" > username:
</label > <input type ="text" name ="name" tabindex ="1" > </p > <p > <label for ="birthday" > birthday:
</label > <input type ="text" name ="birthday" tabindex ="2" /> </p > <p > <label for ="sex" > sex:
</label > <select name ="sex" tabindex ="3" > <option value ="1" > 男
</option > <option value ="2" > 女
</option > </select > </p > <p > <label form ="address" > address:
</label > <input type ="text" name ="address" tabindex ="4" > </p > <p id ="buttons" > <input type ="reset" tabindex ="5" > <input type ="submit" tabindex ="6" value ="Add User" > </p > </form > </fieldset >
</div >
</body >
</html >
@RequestMapping (
"/add_user.do" )
public String
addUser (User user){service.addUser(user);
return "redirect: users.do" ;
}
请求参数解析
在传统的Servlet编程中, 可以使用HttpServletRequest的getParameter()方法来获取请求参数值, 而在Spring MVC中, 它会调用请求参数解析组件 将客户端传过来的String字符串 解析为指定的Java对象 并传递给Controller, 这个过程称为请求参数解析 .
Spring MVC默认提供了很多参数解析组件 , 因此Controller的请求处理方法默认就可以接收很多不同类型:
JavaEEJavaSESpring ServletRequest / HttpServletRequest InputStream / Reader WebRequest / NativeWebRequest ServletResponse / HttpServletResponse OutputStream / Writer Model / ModelMap HttpSession 命令或表单对象 (如String / Integer / User) RedirectAttributes HttpEntity<?> Array / List / Map Errors / BindingResult 带@PathVariable / @MatrixVariable注解的对象 @RequestParam / @RequestHeader / @RequestBody / @RequestPart Principal / Locale SessionStatus UriComponentsBuilder
注: 路径变量映射 (路径变量类似于请求参数, 但没有key部分, 只是一个值, 详细可参考博客Spring MVC URL 路径映射).
ModelAttribute
Spring MVC会在每次调用请求处理方法时都创建一个Model对象, 若打算使用该实例, 则可以在方法的形参添加一个Model形参. 其实还可以使用@ModelAttribute注解来访问Model实例: 使用@ModelAttribute注解标注参数或方法,该方法会将其输入的或创建的参数对象添加到Model对象中:
@RequestMapping (
"/check_id.do" )
public String
checkId (@
ModelAttribute ("id") String id, Model model){
return "check_id" ;
}
String实例将以id做key添加到Model对象中(如果key未命名,则默认使用类型的名称(如string)做key).
@ModelAttribute标注方法 非请求处理方法 : 被@ModelAttribute标注的方法会在每次调用Controller的请求处理方法时调用.该方法可以返回对象或void: 如果返回对象, 该对象会自动添加到Model中:
@ModelAttribute
private List<User>
addUser () {
return service.getAllUsers();
}
若返回void, 则必须添加一个Model类型参数, 自行将实例添加到Model中:
@ModelAttribute
private void addUser (Model model) {model.addAttribute(
"users" , service.getAllUsers());
}
重定向与Flash属性
使用重定向的一个重要场景是避免用户重新加载页面再次调用相同动作 . 比如add_user.do: 当用户提交表单时会将用户信息插入数据库. 但如果在提交表单后重新加载页面, add_user.do会被再次调用, 相同的用户可能会被再次添加.为了避免这种情况, 最好的办法是在提交表单后将用户重定向到一个不同的页面,这个页面任意重新加载都没有副作用.
但使用重定向的一个不便之处在于: 无法轻松的给目标页面传值 . 如果采用转发, 可属性添加到Model, 使得目标视图可以轻松访问. 但用户重定向需要经过客户端, 所以Model的一切内容都会在重定向中丢失. 幸运的是, 在Spring 3.1之后,可以通过Flash属性提供重定向传值的方法:
要使用Flash属性, 必须要有<annotation-driven/>注解驱动支持, 然后在方法上添加一个新的参数类型RedirectAttributes:
@RequestMapping (
"/add_user.do" )
public String
addUser (User user, RedirectAttributes attributes){service.addUser(user);attributes.addAttribute(
"message" ,
"new user has been saved to DB." );
return "redirect: /views/message.vm" ;
}
Controller返回值
应用了@Controller与@RequestMapping注解之后,Controller不再需要implements特定的接口, 因此Controller的返回值也变得多种多样:
返回值描述 ModelAndView 包含视图名与Model数据 Model Map 包含模型的属性 View String 代表逻辑视图名 void 可以在参数中传入request/response完成对参数的解析, 对客户端的响应 HttpEntity/ResponseEntity 提供对Servlet的访问, 以响应HTTP头部和内容 Callable DeferredResult 其他任意类型 常与响应JSON/XML结合
新人创作打卡挑战赛 发博客就能抽奖！定制产品红包拿不停！
总结
以上是生活随笔 为你收集整理的Spring MVC 实践 - Base 的全部内容，希望文章能够帮你解决所遇到的问题。
如果觉得生活随笔 网站内容还不错，欢迎将生活随笔 推荐给好友。
