jackson简单使用案例

新建Maven项目导入依赖包：jakson

 <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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <groupId>henu.yyq</groupId>
     <artifactId>mytest</artifactId>
     <version>0.0.1-SNAPSHOT</version>

     <dependencies>
         <!-- jakson依赖包 因为jackson-databind依赖core和annotation俩jar包，所以maven会自动导入-->
         <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
             <version>2.9.4</version>
         </dependency>
     </dependencies>

         <!-- Jre版本号 -->
     <build>
         <plugins>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.7.0</version>
                 <configuration>
                     <source>1.8</source>
                     <target>1.8</target>
                 </configuration>
             </plugin>
         </plugins>
     </build>
 </project>    

实体类准备

 package henu.yyq.jakson;

 import java.util.Date;

 import com.fasterxml.jackson.annotation.JsonFormat;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonProperty;

 //空值不序列化：ignoreUnknown=true
 //忽略字段：value={"id", ...}
 @JsonIgnoreProperties(ignoreUnknown=true, value={"id"})
 public class Exam {
     private Integer id;

     private String subject;

     @JsonFormat(pattern="yyyy-MM-dd HH:mm:ss")
     private Date starttime;

     //类型转换
     @JsonFormat(pattern="yyyy-MM-dd HH:mm:ss")
     private Date endtime;

     private String state;

     //声明别名
     @JsonProperty("teacherId")
     private String t_id;

     public String getT_id() {
         return t_id;
     }

     public void setT_id(String t_id) {
         this.t_id = t_id;
     }

     public Integer getId() {
         return id;
     }

     public void setId(Integer id) {
         this.id = id;
     }

     public String getSubject() {
         return subject;
     }

     public void setSubject(String subject) {
         this.subject = subject == null ? null : subject.trim();
     }

     public Date getStarttime() {
         return starttime;
     }

     public void setStarttime(Date starttime) {
         this.starttime = starttime;
     }

     public Date getEndtime() {
         return endtime;
     }

     public void setEndtime(Date endtime) {
         this.endtime = endtime;
     }

     public String getState() {
         return state;
     }

     public void setState(String state) {
         this.state = state == null ? null : state.trim();
     }

     @Override
     public String toString() {
         return "Exam [subject=" + subject + ", starttime=" + starttime + ", state=" + state + "]";
     }

 }

 package henu.yyq.jakson;

 import java.util.List;
 import java.util.Map;

 public class TT {

     private List<Map> lm;

     public List<Map> getLm() {
         return lm;
     }

     public void setLm(List<Map> lm) {
         this.lm = lm;
     }

     @Override
     public String toString() {
         return "TT [lm=" + lm + "]";
     }

 }

工具类以及测试

 package henu.yyq.jakson;

 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import org.junit.Test;

 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.ObjectMapper;

 /**
  * @ClassName: JsonUtil <br/>
  * @Describtion: JSON与Java Bean之间的转换. <br/>
  * @date: 2018年4月17日 下午10:29:39 <br/>
  * @author Beats <br/>
  * @version v1.0
  */
 public class JsonUtil {

      // 定义ObjectMapper对象，用于数据转换
     private static final ObjectMapper mapper = new ObjectMapper();

     /**
      * getJSON:(对象转换成JSON). <br/>
      * @param bean
      * @return String
      */
     public static String getJson(Object object) {
         try {
             return mapper.writeValueAsString(object);
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * getBean:(JSON字符串转对象). <br/>
      * @param json
      * @param t
      * @return T
      */
     public static <T> T getBean(String json, Class<T> t) {
         try {
             return mapper.readValue(json, t);
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * jsonToObject:(JSON字符串转对象). <br/>
      * @param json
      * @param t
      * @return T
      */
     public static <T> List<T> getBeanList(String json, Class<T> beanType) {
         try {
             //方案一：
 //            JavaType javaType = mapper.getTypeFactory().constructCollectionType(List.class, beanType);
             //方案二：
             JavaType javaType = mapper.getTypeFactory().constructParametricType(List.class, beanType);
             return mapper.readValue(json, javaType);
             //方案三
 //            TypeReference<T> typeReference = new TypeReference<T>() {};
 //            return mapper.readValue(json, typeReference);
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
     }

     @Test
     public void testGetJson() {
         //简单类型
         Exam e = new Exam();
         e.setId(100);
         e.setSubject("English");
         e.setState("Created");
         e.setStarttime(new Date());
         e.setEndtime(new Date());
         e.setT_id("1234567890");

         String json = JsonUtil.getJson(e);
         System.out.println(json);

         //复杂类型
         TT t = new TT();

         List<Map> l = new ArrayList<Map>();
         Map m = new HashMap();
         m.put("A", "what's your name");
         l.add(m);
         Map m2 = new HashMap();
         m2.put("B", "what's your mather");
         l.add(m2);

         t.setLm(l);

         String res = JsonUtil.getJson(t);
         System.out.println(res);
     }

     @Test
     public void testGetBean() {
         String json = "{\"subject\":\"English\",\"starttime\":\"2018-04-17 15:05:01\",\"endtime\":\"2018-04-17 15:05:01\",\"state\":\"Created\",\"teacherId\":\"1234567890\"}";
         Exam e = JsonUtil.getBean(json, Exam.class);
         System.out.println(e.toString());

         String json2 = "{\"lm\":[{\"A\":\"what's your name\"},{\"B\":\"what's your mather\"}]}";
         TT t = JsonUtil.getBean(json2, TT.class);
         System.out.println(t);
     }

     @Test
     public void testGetBeanList() {
         String json = "[{\"subject\":\"English\",\"starttime\":\"2018-04-17 15:05:01\",\"endtime\":\"2018-04-17 15:05:01\",\"state\":\"Created\",\"teacherId\":\"1234567890\"},{\"subject\":\"English\",\"starttime\":\"2018-04-17 15:05:01\",\"endtime\":\"2018-04-17 15:05:01\",\"state\":\"Created\",\"teacherId\":\"1234567890\"}]";
         List<Exam> es = JsonUtil.getBeanList(json, Exam.class);
         System.out.println(es);

     }
 }

结果自己试试就知道了