关于Jackson2.x中com.fasterxml.jackson包的用法

Jackson应该是目前最好的json解析工具了，之前一直用的是org.codehaus.jackson包中的工具，使用的

包是jackson-all-1.9.11.jar。

最近发现Jackson升级到2.2.3了，出于好奇，准备下载来测试一下，于是在官网下了一个jackson-core-2.2.3

的jar包，发现使用的包名都变成了com.fasterxml.jackson，而且没有找到ObjectMapper对象，以为是整个

设计全变了，看了一下jackson-core的文档，发现有个com.fasterxml.jackson.core.JsonFactory对象，

于是用其来构造com.fasterxml.jackson.core.JsonGenerator，调用writeObject(pojo)方法时

报pojo不是ObjectCodec对象的错误……

最后经过一番检查才发现是包没有导全的原因，Jackson2.2.3是有jackson-core-2.2.3、jackson-annotations-2.2.3、

jackson-databind-2.2.3三个包的，新的ObjectMapper对象在jackson-databind-2.2.3包中，具体使用实例如下。

        =====文件名：JacksonCoreTest.java=====import com.fasterxml.jackson.databind.ObjectMapper;import java.io.IOException;import java.util.ArrayList;import java.util.HashMap;/** * * @author yetao */public class JacksonCoreTest {    public static void main(String[] args) throws IOException{        ArrayList<String> lists = new ArrayList();        lists.add("testlist01");        lists.add("testlist02");        HashMap<String,String> maps = new HashMap();        maps.put("mapkey01","mapvalue01");        maps.put("mapkey02","mapvalue02");        User user1 = new User();        user1.setListinfo(lists);        user1.setMapinfo(maps);        user1.setNumber(100);        user1.setUid(10);        user1.setUname("yetao");        user1.setUpwd("666");        ObjectMapper mapper = new ObjectMapper();        // 仅输出一行json字符串        mapper.writeValue(System.out, user1);        // 将字符串美化成多行        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user1));    }}

        =====文件名：User.java=====import java.util.ArrayList;import java.util.HashMap;public class User {    private int uid;    private String uname;    private String upwd;    private double number;    private ArrayList<String> listinfo;    private HashMap<String,String> mapinfo;    @Override    public String toString(){        StringBuilder sb = new StringBuilder();        sb.append("uid:").append(uid).append("\n");        sb.append("uname:").append(uname).append("\n");        sb.append("upwd:").append(upwd).append("\n");        sb.append("number:").append(number).append("\n");        sb.append("listinfo:").append("[");        for(String info:listinfo){            sb.append(info).append(";");        }        sb.append("]\n");        sb.append("mapinfo:").append("[");        for(String key:mapinfo.keySet()){            sb.append(key).append(":").append(mapinfo.get(key)).append(";");        }        sb.append("]\n");        return sb.toString();    }    public double getNumber() {        return number;    }    public void setNumber(double number) {        this.number = number;    }    public int getUid() {        return uid;    }    public void setUid(int uid) {        this.uid = uid;    }    public String getUname() {        return uname;    }    public void setUname(String uname) {        this.uname = uname;    }    public String getUpwd() {        return upwd;    }    public void setUpwd(String upwd) {        this.upwd = upwd;    }    /**     * @return the listinfo     */    public ArrayList<String> getListinfo() {        return listinfo;    }    /**     * @param listinfo the listinfo to set     */    public void setListinfo(ArrayList<String> listinfo) {        this.listinfo = listinfo;    }    /**     * @return the mapinfo     */    public HashMap<String,String> getMapinfo() {        return mapinfo;    }    /**     * @param mapinfo the mapinfo to set     */    public void setMapinfo(HashMap<String,String> mapinfo) {        this.mapinfo = mapinfo;    }}

美化成多行后的输出如下：
{  "uid" : 10,  "uname" : "yetao",  "upwd" : "666",  "number" : 100.0,  "listinfo" : [ "testlist01", "testlist02" ],  "mapinfo" : {    "mapkey02" : "mapvalue02",    "mapkey01" : "mapvalue01"  }}