【SpringMVC】09 对JSON的应用

前面JavaWeb的JSON回顾：

https://www.cnblogs.com/mindzone/p/12820877.html

上面的这个帖子我都还没有实际写进Servlet使用，要Mark一下了

---

我们配置一个演示的Bean

package cn.dai.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author ArkD42
 * @file SpringMVC
 * @create 2020 - 05 - 07 - 15:06
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
    private String name;
    private Integer age;
    private Boolean gender;
}

编写控制器

@Controller
public class JsonController {

    @GetMapping("/json01")
    public String json01(Model model){

        Person person = new Person("阿强", 22, true);

        model.addAttribute("msg",person.toString());

        return "test";
    }
}

测试我们的响应结果是否会乱码

然后导入Maven坐标

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.11.0</version>
        </dependency>

使用Jackson

package cn.dai.controller;

import cn.dai.pojo.Person;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

import java.util.Arrays;

/**
 * @author ArkD42
 * @file SpringMVC
 * @create 2020 - 05 - 07 - 15:06
 */
@Controller
public class JsonController {

    @GetMapping("/json01")
    public String json01(Model model) throws JsonProcessingException {

        Person person = new Person("阿强", 22, true);

        ObjectMapper objectMapper = new ObjectMapper();

        String s = objectMapper.writeValueAsString(person);

        model.addAttribute("msg", Arrays.toString(new String[]{s,"\n",person.toString()}));

        return "test";
    }
}

访问测试

注意要记得再Web包里面导入Jackson的依赖，

不然会出现找不到Bean异常

测试单个的JSON返回

也是没有问题的，不过这样我也就没有办法演示JSON乱码的问题了

针对JSON乱码的问题，可以使用一个Produces属性

是@RequestMapping注解中的属性

或者使用SpringMVC原生xml配置

Bean方式配置，如果无效，可以尝试放在注解驱动的外面

<?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
"
>
    <!-- 目录扫描的方式注册Bean -->
    <context:component-scan base-package="cn.dai.controller" />
    <!-- 默认的Servlet处理器 不处理静态资源-->
    <mvc:default-servlet-handler />
    <!-- MVC 注解驱动支持-->
    <mvc:annotation-driven>

        <!-- 解决JSON乱码 -->
        <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>

    <!-- 视图解析器 -->
    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>

</beans>

对时间的JSON转换，这是使用LocalDateTime的API

    @GetMapping("/json02")
    public String json02(Model model) throws JsonProcessingException {

        ObjectMapper objectMapper = new ObjectMapper();

        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);

        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);

        String format = dateTimeFormatter.format(now);

        String nows = objectMapper.writeValueAsString(now);

        objectMapper.writeValueAsString(format);

        model.addAttribute("msg", "时间转换测试");
        model.addAttribute("now", now);
        model.addAttribute("nows", nows);
        model.addAttribute("format", format);

        /*
        时间转换测试
        2020-05-07T16:03:07.177
        {"month":"MAY","year":2020,"dayOfYear":128,"dayOfMonth":7,"hour":16,"minute":3,"monthValue":5,"nano":177000000,"second":7,"dayOfWeek":"THURSDAY","chronology":{"id":"ISO","calendarType":"iso8601"}}
        2020-5-7
         */

        return "time";
    }

然后是原生Date & SimpleDateFormat

    @GetMapping("/json03")
    public String json03(Model model) throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();

        Date date = new Date();

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        String format = simpleDateFormat.format(date);

        objectMapper.writeValueAsString(format);

        return "time";
    }

---

Fastjson

Maven坐标

<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.68</version>
</dependency>

    @GetMapping("/json04")
    public String json04(Model model) {

        String s = JSON.toJSONString(new Date());

        model.addAttribute("msg", s);
        return "time";
    }