本文介绍了SpringMVC的集成步骤，包括在pom.xml引入jar包，配置applicationContext-mvc.xml和web.xml。重点解决了NoSession问题，即在使用SpringMVC与JPA集成时遇到的过早关闭EntityManager(Session)导致的序列化错误，提出了通过自定义ObjectMapper并配置到Spring上下文的解决策略。
SpringMvc的集成&web.xml解决noSession
1.在pom.xml引入相应jar包
<!-- 引入web前端的支持 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${org.springframework.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${org.springframework.version}</version>
</dependency>
2.配置applicationContext-mvc.xml
可以为SpringMVC单独配置一个Xml,让它与核心applicationContext.xml分开。让xml的配置成为模块化配置。
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
">
<!-- 对静态资源进行放行 -->
<mvc:default-servlet-handler />
<!-- 扫描controller部分的包 -->
<!-- @Component组件, @Repository持久层, @Service业务逻辑层, and @Controller控制器 -->
<context:component-scan base-package="cn.itsource.pss.web" />
<!-- 添加mvc对@RequestMapping等注解的支持 -->
<mvc:annotation-driven />
<!-- ViewResolver 视图解析器 (struts2视图类型类似) -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!-- 设置视图路径的前后缀，该配置可以让我们写视图路径的时候更简单。 -->
<!-- 希望跳转jsp是[/WEB-INF/views/前缀][xxx变量][.jsp后缀] -->
<!-- * @see #setPrefix -->
<property name="prefix" value="/WEB-INF/views/" />
<!-- * @see #setSuffix -->
<property name="suffix" value=".jsp" />
</bean>
<!-- 错误：提示告诉开发者你没有配置文件上传解析器。 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- 设置上传文件的最大尺寸为1MB -->
<property name="maxUploadSize">
<value>1048576</value>
</property>
</bean>
</beans>
3…配置web.xml
3.1修改版本
如果web.xml的版本是2.3的，那请将它的版本修改成2.4及以上版本，因为这个版本不支持EL表达式。
以下为正确的版本：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
</web-app>
3.2.完成applicationContext.xml的配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/x8ml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
<!-- 读取SpringMVC -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<!-- 启动Spring的监听器 -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!-- 配置核心控制器-->
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<!-- 告诉SpringMVC到哪里去找配置文件 -->
<param-name>contextConfigLocation</param-name>
<!-- 注意:这里只读取springmvc的xml -->
<param-value>classpath:applicationContext-mvc.xml</param-value>
</init-param>
<!-- Servlet默认在每一次访问的时候创建 -->
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!-- 配置解决中文乱码的问题 -->
<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
4.创建Controller与employee.jsp页面
4.1.EmployeeController
package cn.itsource.pss.controller;
import cn.itsource.pss.domain.Employee;
import cn.itsource.pss.service.IEmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import java.util.List;
@Controller
@RequestMapping("/employee")
public class EmployeeController {
@Autowired
private IEmployeeService employeeService;
@RequestMapping("/index")
public String index() {
//根据配置，这里会跳到/WEB-INF/views/employee/employee.jsp页面
return "employee/employee";
}
@RequestMapping("/list")
@ResponseBody
public List<Employee> list(){
return employeeService.findAll();
}
}
4.2.employee.jsp页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>访问成功</h1>
</body>
</html>
5.功能测试
配置：File > Project Structure > Artifacts > 在右侧Output Layout右击项目名，选择Put into Output Root
输入路径 http://localhost/employee/index 查看是否访问成功
输入路径 http://localhost/employee/list 查看是否返回数据
如果访问没有问题，就代表集成已完成！
7.No serializer
noSession:过早关闭了EntityManager(Session)
No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) )
这个错是SpringMVC与Jpa集成的时候(有懒加载)就会出现这个问题。因为你需要序列化对象有一个属性是一类类型，而你使用了Hibernate的延迟加载所以这里是个Hibernate的代理对象。该代理对象有些属性不能被序列化所以会报错。
在类上加属性：生成的时候把这个字段忽略了：
@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler","fieldHandler"})
解决方案：
第一步：创建一个新的类(重写com.fasterxml.jackson.databind.ObjectMapper)
package cn.itsource.pss.common;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
public class CustomMapper extends ObjectMapper {
public CustomMapper() {
this.setSerializationInclusion(JsonInclude.Include.NON_NULL);
// 设置 SerializationFeature.FAIL_ON_EMPTY_BEANS 为 false
this.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
}
}
第二步：在applicationContext-mvc.xml中配置
<!-- Spring MVC 配置 -->
<mvc:annotation-driven>
<mvc:message-converters>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>application/json; charset=UTF-8</value>
<value>application/x-www-form-urlencoded; charset=UTF-8</value>
</list>
</property>
<!-- No serializer:配置 objectMapper 为我们自定义扩展后的 CustomMapper,解决了返回对象有关系对象的报错问题 -->
<property name="objectMapper">
<bean class="cn.itsource.pss.common.CustomMapper"></bean>
</property>
</bean>
</mvc:message-converters>
</mvc:annotation-driven>
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