• 概述
• JacksonTest
• AccountBean
• Birthday

概述

原文链接:http://blog.csdn.net/u011506468/article/details/47342667

最近用到了ObjectMapper，做了些实验。主要有以下一些转换方式：

• JavaBean(Entity/Model)转换成JSON
• 将Map集合转换成Json字符串
• 将List集合转换成json
• 将json字符串转换成JavaBean对象
• 将json字符串转换成List集合
• 将json字符串转换成List集合
• Json字符串转换成Array数组
• Json字符串转换成Map集合

代码如下，全部copy过去即可

JacksonTest

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonTest {
    private JsonGenerator jsonGenerator = null;
    private ObjectMapper objectMapper = null;
    private AccountBean bean = null;

    public static void main (String[] args) {
        JacksonTest test = new JacksonTest();
        test.init();
        /* JavaBean(Entity/Model)转换成JSON */
        //test.writeEntityJSON();
        /* 将Map集合转换成Json字符串 */
        //test.writeMapJSON();
        /* 将List集合转换成json */
        //test.writeListJSON();
        /* 将json字符串转换成JavaBean对象 */
        //test.readJson2Entity();
        /* 将json字符串转换成List<Map>集合 */
        //test.readJson2List();
        /*将json字符串转换成List<T>集合*/
        //test.readJson2ListT();
        /*  Json字符串转换成Array数组 */
        //test.readJson2Array();
        /* Json字符串转换成Map集合 */
        test.readJson2Map();

        test.destory();
    }
    /* Json字符串转换成Map集合 */
    public void readJson2Map() {
        String json = "{\"success\":true,\"A\":{\"address\": \"address2\",\"name\":\"haha2\",\"id\":2,\"email\":\"email2\"},"+
                    "\"B\":{\"address\":\"address\",\"name\":\"haha\",\"id\":1,\"email\":\"email\"}}";
        try {
            Map<String, Map<String, Object>> maps = objectMapper.readValue(json, Map.class);
            System.out.println(maps.size());
            Set<String> key = maps.keySet();
            Iterator<String> iter = key.iterator();
            while (iter.hasNext()) {
                String field = iter.next();
                System.out.println(field + ":" + maps.get(field));
            }
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /*  Json字符串转换成Array数组 */
    public void readJson2Array() {
        String json = "[{\"address\": \"address2\",\"name\":\"haha2\",\"id\":2,\"email\":\"email2\"},"+
                "{\"address\":\"address\",\"name\":\"haha\",\"id\":1,\"email\":\"email\"}]";
        try {
            AccountBean[] arr = objectMapper.readValue(json, AccountBean[].class);
            System.out.println(arr.length);
            for (int i = 0; i < arr.length; i++) {
                System.out.println(arr[i]);
            }

        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /*将json字符串转换成List<T>集合*/
    public void readJson2ListT() {
        String json = "[{\"address\": \"address2\",\"name\":\"haha2\",\"id\":2,\"email\":\"email2\"},"+
                    "{\"address\":\"address\",\"name\":\"haha\",\"id\":1,\"email\":\"email\"}]";
        try {
            List<AccountBean> list = objectMapper.readValue(json, new TypeReference<List<AccountBean>>(){} );
            System.out.println(list.size());
            for (int i = 0; i < list.size(); i++) {
                System.out.println(list.get(i));
            }
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /* 将json字符串转换成List<Map>集合 */
    public void readJson2List() {
        String json = "[{\"address\": \"address2\",\"name\":\"haha2\",\"id\":2,\"email\":\"email2\"},"+
                    "{\"address\":\"address\",\"name\":\"haha\",\"id\":1,\"email\":\"email\"}]";
        try {
            List<LinkedHashMap<String, Object>> list = objectMapper.readValue(json, List.class);
            System.out.println(list.size());
            for (int i = 0; i < list.size(); i++) {
                Map<String, Object> map = list.get(i);
                Set<String> set = map.keySet();
                for (Iterator<String> it = set.iterator();it.hasNext();) {
                    String key = it.next();
                    System.out.println(key + ":" + map.get(key));
                }
            }
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /* 将json字符串转换成JavaBean对象 */
    public void readJson2Entity() {
        String json = "{\"address\":\"address\",\"name\":\"haha\",\"id\":1,\"email\":\"email\"}";
        try {
            AccountBean acc = objectMapper.readValue(json, AccountBean.class);
            System.out.println(acc.getName());
            System.out.println(acc);
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /* 将List集合转换成json */
    public void writeListJSON() {
        try {
            List<AccountBean> list = new ArrayList<AccountBean>();
            list.add(bean);

            bean = new AccountBean();
            bean.setId(2);
            bean.setAddress("address2");
            bean.setEmail("email2");
            bean.setName("haha2");
            list.add(bean);

            System.out.println("jsonGenerator");
            //list转换成JSON字符串
            jsonGenerator.writeObject(list);
            System.out.println();
            System.out.println("ObjectMapper");
            //用objectMapper直接返回list转换成的JSON字符串
            System.out.println("1###" + objectMapper.writeValueAsString(list));
            System.out.print("2###");
            //objectMapper list转换成JSON字符串
            objectMapper.writeValue(System.out, list);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /* 将Map集合转换成Json字符串 */
    public void writeMapJSON() {
        try {
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("name", bean.getName());
            map.put("account", bean);
            bean = new AccountBean();
            bean.setAddress("china-Beijin");
            bean.setEmail("[email protected]");
            map.put("account2", bean);

            System.out.println("jsonGenerator");
            jsonGenerator.writeObject(map);
            System.out.println("");

            System.out.println("objectMapper");
            objectMapper.writeValue(System.out, map);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /* JavaBean(Entity/Model)转换成JSON */
    public void writeEntityJSON() {

        try {
            System.out.println("jsonGenerator");
            //writeObject可以转换java对象，eg:JavaBean/Map/List/Array等
            jsonGenerator.writeObject(bean);
            System.out.println();

            System.out.println("ObjectMapper");
            //writeValue具有和writeObject相同的功能
            objectMapper.writeValue(System.out, bean);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /* 初始化 */
    public void init() {
        bean = new AccountBean();
        bean.setAddress("china-Guangzhou");
        bean.setEmail("ho[email protected]");
        bean.setId(1);
        bean.setName("hoojo");
        objectMapper = new ObjectMapper();
        try {
            jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(System.out, JsonEncoding.UTF8);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /* 释放资源 */
    public void destory() {
        try {
            if (jsonGenerator != null) {
                jsonGenerator.flush();
            }
            if (!jsonGenerator.isClosed()) {
                jsonGenerator.close();
            }
            jsonGenerator = null;
            objectMapper = null;
            bean = null;
            System.gc();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

AccountBean

public class AccountBean {
    private int id;
    private String name;
    private String email;
    private String address;
    private Birthday birthday;

    //getter、setter

    @Override
    public String toString() {
        return this.name + "#" + this.id + "#" + this.address + "#" + this.birthday + "#" + this.email;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Birthday getBirthday() {
        return birthday;
    }

    public void setBirthday(Birthday birthday) {
        this.birthday = birthday;
    }

}

Birthday

public class Birthday {
    private String birthday;

    public Birthday(String birthday) {
        super();
        this.birthday = birthday;
    }

    //getter、setter

    public Birthday() {}

    @Override
    public String toString() {
        return this.birthday;
    }
}

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