jakeson的使用
先导入jakeson的包
<dependencies>
<!--将字符串转换成JSON格式-->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.13.1</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
</dependency>
</dependencies>
配置web.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<!--1.注册servlet-->
<servlet>
<servlet-name>SpringMVC</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--通过初始化参数指定SpringMVC配置文件的位置，进行关联-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
<!-- 启动顺序，数字越小，启动越早 -->
<load-on-startup>1</load-on-startup>
</servlet>
<!--所有请求都会被springmvc拦截 -->
<servlet-mapping>
<servlet-name>SpringMVC</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>encoding</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>
</filter>
<filter-mapping>
<filter-name>encoding</filter-name>
<url-pattern>/</url-pattern>
</filter-mapping>
</web-app>
配置springmvc-servlet.xml
<?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
https://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
https://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!-- 自动扫描指定的包，下面所有注解类交给IOC容器管理 -->
<context:component-scan base-package="com.Google.controller"/>
<!-- 视图解析器 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
id="internalResourceViewResolver">
<!-- 前缀 -->
<property name="prefix" value="/WEB-INF/jsp/" />
<!-- 后缀 -->
<property name="suffix" value=".jsp" />
</bean>
</beans>
编写实体类
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
private String name;
private int age;
private String Sex;
}
编写Controller，传递一个对象
package com.Google.controller;
import com.Google.pojo.User;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
//@Controller
@RestController//这个注解不会走视图解析器，会直接返回一个字符串
public class jsonController {
@RequestMapping("/j1")
//@ResponseBody//这个注解配合@Controller一起使用达到RestController的效果
public String json1() throws JsonProcessingException {
//
ObjectMapper mapper = new ObjectMapper();
User user = new User("Spring", 2, "女");
String str = mapper.writeValueAsString(user);
return str;
}
}
后端一般就是传字符串给前端，所以以后一般直接使用RestController
这里没有配置传输JSON乱码问题
可以使用RequestMapping
//produces:指定响应体返回类型和编码
@RequestMapping(value = "/json1",produces = "application/json;charset=utf-8")
最好就是同一处理(在spring中处理)
<!--配合Jakeson，解决JSON乱码问题-->
<mvc:annotation-driven>
<mvc:message-converters register-defaults="true">
<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>
传递一个数组
//传递一个数组
@RequestMapping("/j2")
public String json2() throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
List<User> users = new ArrayList<>();
User user = new User("Spring", 2, "女");
User user1 = new User("Spring", 2, "女");
User user2 = new User("Spring", 2, "女");
User user3 = new User("Spring", 2, "女");
users.add(user);
users.add(user1);
users.add(user2);
users.add(user3);
return mapper.writeValueAsString(users);
}
传递一个时间对象
//传递一个时间对象
@RequestMapping("/j3")
public String json3() throws JsonProcessingException {
Date date = new Date();
return new ObjectMapper().writeValueAsString(date);
}
时间对象返回的结果是一个时间戳
我们需要更改一下它的格式
1、使用java纯代码
//传递一个时间对象
@RequestMapping("/j3")
public String json3() throws JsonProcessingException {
Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");
String format = dateFormat.format(date);
return new ObjectMapper().writeValueAsString(format);
}
结果
2、使用jackson取消timestamps形式 ， 自定义时间格式
@RequestMapping("/j3")
public String json3() throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
//将时间戳的方式关闭
mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
Date date = new Date();
//自定义时间格式
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");
mapper.setDateFormat(dateFormat);
return mapper.writeValueAsString(date);
}
结果
可以将重复使用的代码包装成一个类，来实现代码的复用(编写这类代码，思想很重要啊)
public class JsonUtils {
public static String getJson(Object object) {
return getJson(object,"yyyy-MM-dd HH:mm:ss");
}
public static String getJson(Object object,String dateFormat) {
ObjectMapper mapper = new ObjectMapper();
//不使用时间差的方式
mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
//自定义日期格式对象
SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
//指定日期格式
mapper.setDateFormat(sdf);
try {
return mapper.writeValueAsString(object);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
return null;
}
}
