com.fasterxml.jackson.databind.ObjectMapper操作對象和集合的一些相互轉換用法

標籤：objectmapp   json   對象轉json   json轉list   json轉map   

• 概述
• JacksonTest
• AccountBean
• Birthday

概述

原文連結:http://blog.csdn.net/u011506468/article/details/47342667
最近用到了ObjectMapper，做了些實驗。主要有以下一些轉換方式：

• JavaBean(Entity/Model)轉換成JSON
• 將Map集合轉換成Json字串
• 將List集合轉換成json
• 將json字串轉換成JavaBean對象
• 將json字串轉換成List集合
• 將json字串轉換成List集合
• Json字串轉換成Array數組
• Json字串轉換成Map集合

代碼如下，全部copy過去即可

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)轉換成JSON */          //test.writeEntityJSON();        /* 將Map集合轉換成Json字串 */        //test.writeMapJSON();        /* 將List集合轉換成json */        //test.writeListJSON();        /* 將json字串轉換成JavaBean對象 */        //test.readJson2Entity();        /* 將json字串轉換成List<Map>集合 */        //test.readJson2List();        /*將json字串轉換成List<T>集合*/        //test.readJson2ListT();        /*  Json字串轉換成Array數組 */        //test.readJson2Array();        /* Json字串轉換成Map集合 */        test.readJson2Map();        test.destory();    }    /* Json字串轉換成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字串轉換成Array數組 */    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();        }    }    /*將json字串轉換成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();        }    }    /* 將json字串轉換成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();        }    }    /* 將json字串轉換成JavaBean對象 */    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();        }    }    /* 將List集合轉換成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轉換成JSON字串            jsonGenerator.writeObject(list);            System.out.println();            System.out.println("ObjectMapper");            //用objectMapper直接返回list轉換成的JSON字串            System.out.println("1###" + objectMapper.writeValueAsString(list));            System.out.print("2###");            //objectMapper list轉換成JSON字串            objectMapper.writeValue(System.out, list);        } catch (IOException e) {            e.printStackTrace();        }    }    /* 將Map集合轉換成Json字串 */    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)轉換成JSON */    public void writeEntityJSON() {        try {            System.out.println("jsonGenerator");            //writeObject可以轉換java對象，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("[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();        }    }    /* 釋放資源 */    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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com.fasterxml.jackson.databind.ObjectMapper操作對象和集合的一些相互轉換用法