Jackson 高性能的JSON处理 ObjectMapper

原文地址 http://blog.csdn.net/wangyang2698341/article/details/8223929 今天自行研究了下json ，感觉非常好用，经过测试比google的GSON快多了
同时Jackson可以轻松的将Java对象转换成json对象和xml文档，同样也可以将json、xml转换成Java对象。功能非常的强悍！
大家也知道，json 在如今互联网时代应用的非常广，因为大家如此的关注，所以对json的解析性能要求也是非常高的。

一、 准备工作
1、 下载依赖库jar包
Jackson的jar all下载地址：http://jackson.codehaus.org/1.7.6/jackson-all-1.7.6.jar
然后在工程中导入这个jar包即可开始工作
官方示例：http://wiki.fasterxml.com/JacksonInFiveMinutes
因为下面的程序是用junit测试用例运行的，所以还得添加junit的jar包。版本是junit-4.2.8
如果你需要转换xml，那么还需要stax2-api.jar
2、 测试类基本代码如下

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/*

* @project java

* @package

* @file Jackson.java

* @version 1.0

* @author 廖益平

* @time 2011-11-8 上午02:59:37

*/

public class Jackson {

/*

*

* Class Descripton goes here.

*

* @class Jackson

* @version 1.0

* @author 廖益平

* @time 2011-11-8 上午02:59:37

*/

public static JsonGenerator jsonGenerator = null;

private static ObjectMapper mapper = new ObjectMapper();

public static void main(String[] args) {

Student student = new Student();

student.setIsstudent(true);

student.setUid(1000);

student.setUname("xiao liao");

student.setUpwd("123");

student.setNumber(12);

Map<String, Student> stuMap = new HashMap<String, Student>();

stuMap.put("1", student);

stuMap.put("2", student);

List<Object> stuList = new ArrayList<Object>();

List<Student> stuList1 = new ArrayList<Student>();

stuList1.add(student);

student= new Student();

student.setIsstudent(false);

student.setUid(200);

student.setUname("xiao mi");

stuList1.add(student);

stuList.add(student);

stuList.add("xiao xin");

stuList.add("xiao er");

stuList.add(stuMap);

//readJson2List();

try {

//readJson2Array();

//writeArray2Json(array);

//writeJson2List();

//writeEntity2Json(student);

writeJson2Entity();

//writeMap2Json(stuMap);

//writeList2Json(stuList1);

} catch (IOException e) {

e.printStackTrace();

}

}

/**

*

* <code>writeEntity2Json</code>

* @description: TODO(实体类转换成json)

* @param object

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeEntity2Json(Object object) throws IOException {

mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"),object );

mapper.writeValue( System.out,object );

}

/**

*

* <code>writeArray2Json</code>

* @description: TODO(数组转换成json数组)

* @param object

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeArray2Json(Object object) throws IOException {

// writeValue具有和writeObject相同的功能

mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"),object );

mapper.writeValue(System.out,object );

}

/**

*

* <code>writeMap2Json</code>

* @description: TODO(map对象转换成json对象)

* @param object

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeMap2Json(Object object) throws IOException {

System.out.println("使用ObjectMapper-----------");

// writeValue具有和writeObject相同的功能

System.out.println("==>"+mapper.writeValueAsString(object));

mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aamap.txt"),object );

mapper.writeValue( System.out , object );

}

/**

*

* <code>writeList2Json</code>

* @description: TODO(list转换成json)

* @param object

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeList2Json(Object object) throws IOException {

System.out.println("==>"+mapper.writeValueAsString(object));

mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aamap.txt"),object );

mapper.writeValue( System.out , object );

}

/**

*

* <code>writeJson2Entity</code>

* @description: TODO(json转换成实体)

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeJson2Entity() throws IOException {

System.out.println("json串转换成entity-------------");

// File file = new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt");

// FileInputStream inputStream = new FileInputStream(file);

// Student student = mapper.readValue(inputStream,Student.class);

// System.out.println(student.toString());

//漂亮输出

//mapper.defaultPrettyPrintingWriter().writeValueAsString(value);

String json = "{\"uid\":1000,\"uname\":\"xiao liao\",\"upwd\":\"123\",\"number\":12.0,\"isstudent\":true}";

Student student1 = mapper.readValue(json,Student.class);

System.out.println("json2:"+student1.toString());

}

/**

*

* <code>writeJson2List</code>

* @description: TODO(json专程list对象)

* @throws IOException

* @since 2011-11-8 廖益平

*/

public static void writeJson2List() throws IOException {

System.out.println("json串转换成entity-------------");

File file = new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt");

FileInputStream inputStream = new FileInputStream(file);

Student student = mapper.readValue(inputStream,Student.class);

System.out.println(student.toString());

String json = "[{\"uid\":1000,\"uname\":\"xiao liao\",\"upwd\":\"123\",\"number\":12.0,\"isstudent\":true},{\"uid\":200,\"uname\":\"xiao mi\",\"upwd\":null,\"number\":0.0,\"isstudent\":false}]";

List<LinkedHashMap<String, Object>> s= mapper.readValue(json,List.class);

for (int i = 0; i < s.size(); i++) {

LinkedHashMap<String, Object> link = s.get(i);

Set<String> key = link.keySet();

for (Iterator iterator = key.iterator(); iterator.hasNext();) {

String string = (String) iterator.next();

System.out.println(string+"==>"+link.get(string));

}

System.out.println("json:"+i+""+s.get(i).toString());

}

}

/**

* JSON转换为List对象

*/

public static void readJson2List() {

String json = "[{\"uid\":1,\"uname\":\"www\",\"number\":234,\"upwd\":\"456\"},"

+ "{\"uid\":5,\"uname\":\"tom\",\"number\":3.44,\"upwd\":\"123\"}]";

try {

List<LinkedHashMap<String, Object>> list = mapper.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();

}

}

/**

* JSON转换为List对象

*/

public static void readJson2Array() {

String json = "[{\"uid\":1,\"uname\":\"www\",\"number\":234,\"upwd\":\"456\"},"

+ "{\"uid\":5,\"uname\":\"tom\",\"number\":3.44,\"upwd\":\"123\"}]";

try {

Student[] students = mapper.readValue(json, Student[].class);

for (Student student : students) {

System.out.println(">"+student.toString());

}

} catch (JsonParseException e) {

e.printStackTrace();

} catch (JsonMappingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

}

打印结果 ：
串转换成entity-------------

json2:uid=1000,name=xiao liao,upwd=123,number=12.0,isStudent=true
writeMap2Json -----------

{"2":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true},"1":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true}}
readJson2Array------------------

>uid=1,name=www,upwd=456,number=234.0,isStudent=false

>uid=5,name=tom,upwd=123,number=3.44,isStudent=false

writeMap2Json -----------

{"2":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true},"1":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true}}
大家逐个自己试试吧 ，上面也是我的测试代码

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实体类：

/*

* @project java

* @package

* @file Student.java

* @version 1.0

* @author 廖益平

* @time 2011-11-8 上午03:01:08

*/

public class Student {

/*

*

* Class Descripton goes here.

*

* @class Student

* @version 1.0

* @author 廖益平

* @time 2011-11-8 上午03:01:08

*/

private int uid;

private String uname;

private String upwd;

private double number;

private boolean isstudent;

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;

}

public double getNumber() {

return number;

}

public void setNumber(double number) {

this.number = number;

}

public boolean isIsstudent() {

return isstudent;

}

public void setIsstudent(boolean isstudent) {

this.isstudent = isstudent;

}

@Override

public String toString() {

return "uid="+uid+",name="+uname+",upwd="+upwd+",number="+number+",isStudent="+isstudent;

}

}