JSON

一、Jackson

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<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.11.2</version>
</dependency>

代码测试：

一、使用@ controller

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package com.saxon.controller;


import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.saxon.pojo.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;



@Controller
public class MyController {
    @PostMapping ("/hello")//详相当于servletmappering
    @ResponseBody
    public String hello (User user, Model model) throws JsonProcessingException {
        ObjectMapper obj = new ObjectMapper ();
        return obj.writeValueAsString (user);
    }
}

@ResponseBody:跳过视图解析器，直接返回结果；

ObjectMapper：转换对象

二、使用@Restcontroller

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@RestController
public class MyController {
    @PostMapping ("/hello")//详相当于servletmappering
    
    public String hello (User user, Model model) throws JsonProcessingException {
        ObjectMapper obj = new ObjectMapper ();
        return obj.writeValueAsString (user);
    }
}

跳过视图解析器直接返回数据；这样的话就可以直接不用@responseBody:

二、关于json的乱码问题的解决：

方法一：

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@RequestMapping(value = "/xx", produces = "application/json;charset=utf-8")

方法二：

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<!--Jackson乱码解决-->
<mvc:annotation-driven>
    <mvc:message-converters>
        <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>

三、日期时间的格式化

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public String hello (User user, Model model) throws JsonProcessingException {
        ObjectMapper obj = new ObjectMapper ();
        obj.configure (SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS,false);
        obj.setDateFormat (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss"));
        return obj.writeValueAsString (new Date ());
    }

第一种方法：

使用原来的日期时间类来格式化我们的时间

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public String hello (User user, Model model) throws JsonProcessingException {
        return new ObjectMapper ().writeValueAsString (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss").format(new Date()));
    }

第二种方法：

配置我们的objectMapper；

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public String hello (User user, Model model) throws JsonProcessingException {
        ObjectMapper obj = new ObjectMapper ();
        obj.configure (SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS,false);
        obj.setDateFormat (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss"));
        return obj.writeValueAsString (new Date ());
    }