Springboot中解析JSON字符串(jackson库ObjectMapper解析JSON字符串)

本文介绍: springboot中通过 jackson 库中的objectmapper 对象实现，对象和JSON相互转化，Li st 集合JSON相互转化，Map和JSON相互转化

1、Obje ctMap per 属于 jackson库的一部分,JSONObje ct 属于 alibaba的fastjson，两者各有优劣，可根据自己的系统环境选择使用哪种技术。

2、目前来看，Jack son 社区相对活跃，Spr in g MVC和Spr in g Bo o t都默认使用Ja ck son。

核心主要有三个部分：

jackson–core(核心包)、jackson–data bind(数据绑定包)、jackson–annotation s(注解包)

//JSONObject依赖包

&lt;dependency&gt;

    <groupId&gt;com.alibaba.fastjson2</groupId>

    <artifactId>fastjson2</artifactId>

    <version>2.0.42</version>

</dependency>

//ObjectMapper依赖包

<dependency>

    <groupId>com.fasterxml.jackson.core</groupId>

    <artifactId>jackson-databind</artifactId>

    <version>2.14.2</version>

</dependency>

ObjectMa p per 通过 writeValue()实现序列化，通过 readValue()实现反序列化。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.17</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.txc</groupId>
    <artifactId>objectmapper</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>objectmapper</name>
    <description>objectmapper</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

案例中使用lombok注解生成get和set方法，也可以直接写get和set方法

@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Student {
    private String stu_id;
    private String stu_name;
}

/**
 * 实现对象和JSON之间互转
 */
@RequestMapping("/jsonObjectChange")
@ResponseBody
public  void  jsonObjectChange() throws Exception{
    ObjectMapper mapper = new ObjectMapper();
    String param = "{"stu_id":"1001","stu_name":"晓春","stu_sex":"男","stu_age":"34","stu_addr":"安徽合肥","stu_pwd":"123456"}";
    //将字符串转换为对象—反序列化过程
    Student student = mapper.readValue(param, Student.class);
    System.out.println("===json转对象==="+student.toString());
    //将对象转化成JSON—序列化过程
    String  json = mapper.writeValueAsString(student);
    System.out.println("===对象转json==="+json);
}

/**
 * 集合和JSON相互转化
 */
@RequestMapping("/listAndJSONChange")
@ResponseBody
public void  arrayToObject() throws Exception{
    Student student1=new Student("1001","晓春1","男","34","安徽合肥","123456");
    Student student2=new Student("1002","晓春2","男","34","安徽合肥","123456");
    ObjectMapper mapper = new ObjectMapper();
    //集合转json
    String param = mapper.writeValueAsString(Arrays.asList(student1,student2));
    System.out.println("==集合转json=="+param);
    //数组json转化成集合
    List<Student> list= mapper.readValue(param, List.class);
    System.out.println("==数组json转集合=="+list);
}

/**
 * map和json相互转化
 */
@RequestMapping("/mapAndJsonChange")
@ResponseBody
public void  mapAndJsonChange() throws Exception{
    ObjectMapper mapper = new ObjectMapper();
    Map<String, Object> map = new HashMap<>();
    map.put("id", "1001");
    map.put("name","晓春");
    map.put("student", new Student("6","6","6","6","6","6"));
    String param = mapper.writeValueAsString(map);
    System.out.println("===map转json==="+param);
    Map<String, Object> resultMap = mapper.readValue(param, Map.class);
    System.out.println("===json转map==="+resultMap);
}

@Configuration
public class ObjectMapperConfig {

    @Bean("objectMapper")
    public ObjectMapper getObjectMapper(){
        ObjectMapper  mapper = new ObjectMapper();
        //属性为NULL 不序列化
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        //属性为默认值不序列化
        mapper.setSerializationInclusion(JsonInclude.Include.NON_DEFAULT);

        //反序列化时,遇到未知属性不报错
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

        //如果是空对象的时候,不抛异常
        mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);

        //修改序列化后日期格式
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

        return mapper;
    }


}