springmvc @RequestBody String类型参数的使用

springmvc @RequestBody String类型参数

通过如下配置：

 <bean id="mappingJacksonHttpMessageConverter"
        class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
      <property name="supportedMediaTypes">
          <list>
              <value>text/html;charset=UTF-8</value>
              <value>application/json;charset=UTF-8</value>
          </list>
      </property>
  </bean>
  <!-- 启动SpringMVC的注解功能，完成请求和注解POJO的映射 -->
  <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"/>
  <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
      <property name="messageConverters">
          <list>
              <ref bean="mappingJacksonHttpMessageConverter"/>
              <!-- JSON转换器 -->
          </list>
      </property>
  </bean>

在spring mvc的Controller层使用@RequestBody接收Content-Type为application/json的数据时，默认支持Map方式和对象方式参数

@RequestMapping(value = "/[code]/saveUser", method = RequestMethod.POST)
  @ResponseBody
  public JsonResult saveUser(@PathVariable("code") Integer code, @RequestBody Map<String, Object> datas,@RequestBody User user) {
  。。。
  }

如果是一个参数时也需要用个Map或者对象处理，使用String会报解析错误，具体看：AbstractJackson2HttpMessageConverter的方法read(Type type, Class

@Override
  public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
          throws IOException, HttpMessageNotReadableException {
      JavaType javaType = getJavaType(type, contextClass);
      return readJavaType(javaType, inputMessage);
  }
  private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) {
      try {
          return this.objectMapper.readValue(inputMessage.getBody(), javaType);
      }
      catch (IOException ex) {
          throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
      }
  }

为了让@RequestBody支持String参数(目前只支持接收单个参数)

重写org.springframework.http.converter.json.MappingJackson2HttpMessageConverter类

package com.test.converter.json
import org.springframework.http.HttpInputMessage;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import java.io.IOException;
import java.lang.reflect.Type;
import java.util.LinkedHashMap;
/**
* 处理@RequestBody注解为String的情况，只支持接收单个参数的情况
* Created by test
* Date:2017/1/4
* Time:17:33
*/
public class CustomerMappingJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {
  @Override
  protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
      Class<?> deseriClazz = getClazz(clazz);
      Object param = super.readInternal(deseriClazz, inputMessage);
      return getTrueObject(clazz, param);
  }
  @Override
  public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
          throws IOException, HttpMessageNotReadableException {
      Type deseriType = getType(type);
      Object param = super.read(deseriType, contextClass, inputMessage);
      return getTrueObject(type, param);
  }
  /**
   * 通过返回参数类型决定是否处理参数，如果是String类型的参数，将解析后的HashMap里的值返回（只支持单个参数）
   *
   * @param type  返回参数类型
   * @param param 参数值
   * @return 实际参数值
   */
  private Object getTrueObject(Type type, Object param) {
      if (type == String.class) {
          Object backParam = null;
          if (param != null && param instanceof LinkedHashMap) {
              LinkedHashMap paramMap = (LinkedHashMap) param;
              if (paramMap.size() == 1) {
                  backParam = paramMap.get(paramMap.keySet().iterator().next());
              }
          }
          param = backParam;
      }
      return param;
  }
  /**
   * 获取解析参数用的Type
   *
   * @param type 参数类型
   * @return
   */
  private Type getType(Type type) {
      Type deseriClazz;
      if (type == String.class) {
          //jackson不支持String默认用LinkedHashMap
          deseriClazz = LinkedHashMap.class;
      } else {
          deseriClazz = type;
      }
      return deseriClazz;
  }
  /**
   * 获取解析参数用的Type
   * @param clazz 参数类型
   * @return
   */
  private Class<?> getClazz(Class<?> clazz) {
      Class<?> deseriClazz;
      if (clazz == String.class) {
          //jackson不支持String默认用LinkedHashMap
          deseriClazz = LinkedHashMap.class;
      } else {
          deseriClazz = clazz;
      }
      return deseriClazz;
  }
}

spring mvc xml配置文件修改：

<bean id="mappingJacksonHttpMessageConverter"
        class="com.test.converter.json.CustomerMappingJackson2HttpMessageConverter">
      <property name="supportedMediaTypes">
          <list>
              <value>text/html;charset=UTF-8</value>
              <value>application/json;charset=UTF-8</value>
          </list>
      </property>
  </bean>

Controller层：

@RequestMapping(value = "/delUser", method = RequestMethod.POST)
  @ResponseBody
  public JsonResult delUser(@RequestBody String id) {
  。。。
  }

springmvc用Map接收请求参数分析

第一种情况，什么也不设置，无参数传递

注解为 @Controller @RequestMapping

springmvc @RequestBody String类型参数的使用

可以看到传递的为SpringMVC的BindingAwareModelMap类型，SpringMVC中的隐含模型就是这个类型，其作用域等价于 request 域，当添加Model、ModelMap参数时，SpringMVC实际传入的就是这个隐含模型；向这个隐含模型种设置值后，在返回的页面中就能通过request域取值。