import com.fasterxml.jackson.annotation.JsonFormat;

import java.util.Date;

public class Person {

    private String name;

    private int age ;

    private String gender;

    //@JsonIgnore // 忽略该属性

    @JsonFormat(pattern = "yyyy-MM-dd")

    private Date birthday;//该属性用来讲解注解的使用

    public Date getBirthday() {

        return birthday;

    }

    public void setBirthday(Date birthday) {

        this.birthday = birthday;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getGender() {

        return gender;

    }

    public void setGender(String gender) {

        this.gender = gender;

    }

    @Override

    public String toString() {

        return "Person{" +

                "name='" + name + '\'' +

                ", age=" + age +

                ", gender='" + gender + '\'' +

                '}';

    }

}

//演示 JSON字符串转为Java对象

    @Test

    public void test5() throws Exception {

       //1.初始化JSON字符串

        String json = "{\"gender\":\"男\",\"name\":\"张三\",\"age\":23}";

        //2.创建ObjectMapper对象

        ObjectMapper mapper = new ObjectMapper();

        //3.转换为Java对象 Person对象

        Person person = mapper.readValue(json, Person.class);

        System.out.println(person);

    }

import cn.itcast.domain.Person;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.junit.Test;

import java.io.FileWriter;

import java.util.*;

public class JacksonTest {

    //Java对象转为JSON字符串

    @Test

    public void test1() throws Exception {

        //1.创建Person对象

        Person p  = new Person();

        p.setName("张三");

        p.setAge(23);

        p.setGender("男");

        //2.创建Jackson的核心对象  ObjectMapper

        ObjectMapper mapper = new ObjectMapper();

        //3.转换

        /*

            转换方法：

                writeValue(参数1，obj):

                    参数1：

                        File：将obj对象转换为JSON字符串，并保存到指定的文件中

                        Writer：将obj对象转换为JSON字符串，并将json数据填充到字符输出流中

                        OutputStream：将obj对象转换为JSON字符串，并将json数据填充到字节输出流中

                writeValueAsString(obj):将对象转为json字符串

         */

        String json = mapper.writeValueAsString(p);//System.out.println(json);//输出结果{"name":"张三","age":23,"gender":"男"}

        //writeValue，自动创建一个a.txt文件，将数据写到d://a.txt文件中

        //mapper.writeValue(new File("d://a.txt"),p);

        
　　　　 //writeValue，将数据关联到Writer中，同上面一样，自动创建一个b.txt文件，将数据写到d://b.txt文件中

        mapper.writeValue(new FileWriter("d://b.txt"),p);

    }
}

 @JsonIgnore // 忽略该属性

 private Date birthday;

@JsonFormat(pattern = "yyyy-MM-dd")

private Date birthday;

    @Test

    public void test2() throws Exception {

        //1.创建Person对象

        Person p = new Person();

        p.setName("张三");

        p.setAge(23);

        p.setGender("男");

        p.setBirthday(new Date());

        //2.转换

        ObjectMapper mapper = new ObjectMapper();

        String json = mapper.writeValueAsString(p);

        System.out.println(json);

　　    //birthday格式化前：{"name":"张三","age":23,"gender":"男","birthday":1530958029263}

　　    //birthday格式化后：{"name":"张三","age":23,"gender":"男","birthday":"2018-07-07"}

    }

 @Test

    public void test3() throws Exception {

        //1.创建Person对象

        Person p = new Person();

        p.setName("张三");

        p.setAge(23);

        p.setGender("男");

        p.setBirthday(new Date());

        Person p1 = new Person();

        p1.setName("张三");

        p1.setAge(23);

        p1.setGender("男");

        p1.setBirthday(new Date());

        Person p2 = new Person();

        p2.setName("张三");

        p2.setAge(23);

        p2.setGender("男");

        p2.setBirthday(new Date());

        //创建List集合

        List<Person> ps = new ArrayList<Person>();

        ps.add(p);

        ps.add(p1);

        ps.add(p2);

        //2.转换

        ObjectMapper mapper = new ObjectMapper();

        String json = mapper.writeValueAsString(ps);

        // [{},{},{}]

        //打印结果[{"name":"张三","age":23,"gender":"男","birthday":"2018-07-07"},{"name":"张三","age":23,"gender":"男","birthday":"2018-07-07"},{"name":"张三","age":23,"gender":"男","birthday":"2018-07-07"}]

        System.out.println(json);

    }

@Test

    public void test4() throws Exception {

        //1.创建map对象

        Map<String,Object> map = new HashMap<String,Object>();

        map.put("name","张三");

        map.put("age",23);

        map.put("gender","男");

        //2.转换

        ObjectMapper mapper = new ObjectMapper();

        String json = mapper.writeValueAsString(map);

        System.out.println(json);//打印结果{"gender":"男","name":"张三","age":23}

    }