springmvc @RequestBody String类型参数的使用

作者：zoyation 时间：2023-03-08 09:30:05　

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>

<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"/>

</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

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。