Fastjson介绍
Fastjson是一个Java语言编写的JSON处理器,由阿里巴巴公司开发。
1、遵循http://json.org标准，为其官方网站收录的参考实现之一。
2、功能qiang打，支持JDK的各种类型，包括基本的JavaBean、Collection、Map、Date、Enum、泛型。
3、无依赖，不需要例外额外的jar，能够直接跑在JDK上。
4、开源，使用Apache License 2.0协议开源。http://code.alibabatech.com/wiki/display/FastJSON/Home
5、具有超高的性能，java世界里没有其他的json库能够和fastjson可相比了。
如果获得Fastjson？
SVN:http://code.alibabatech.com/svn/fastjson/trunk/
WIKI:http://code.alibabatech.com/wiki/display/FastJSON/Home
Issue Tracking:http://code.alibabatech.com/jira/browse/FASTJSON
如果你使用了Maven，maven repository配置如下：
<repository>
<id>opensesame</id>
<name>Alibaba OpenSource Repsoitory</name>
<url>http://code.alibabatech.com/mvn/releases/</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
pom.xml文件中加入依赖依赖：
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.9</version>
</dependency>
如果没有使用maven，可以直接下载：
Binary : http://code.alibabatech.com/mvn/releases/com/alibaba/fastjson/1.1.1/fastjson-1.1.1.jar
Source :http://code.alibabatech.com/mvn/releases/com/alibaba/fastjson/1.1.1/fastjson-1.1.1-sources.jar
Subversion : http://code.alibabatech.com/svn/fastjson/
使用介绍：
Fastjson的最主要的使用入口是com.alibaba.fastjson.JSON
import com.alibaba.fastjson.JSON; public static final Object parse(String text); // 把JSON文本parse为JSONObject或者JSONArray
public static final JSONObject parseObject(String text)； // 把JSON文本parse成JSONObject
public static final <T> T parseObject(String text, Class<T> clazz); // 把JSON文本parse为JavaBean
public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray
public static final <T> List<T> parseArray(String text, Class<T> clazz); //把JSON文本parse成JavaBean集合
public static final String toJSONString(Object object); // 将JavaBean序列化为JSON文本
public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本
public static final Object toJSON(Object javaObject); 将JavaBean转换为JSONObject或者JSONArray。
使用例子：
两个基础类：
public class Student {
private int id;
private String name;
/**
* 默认的构造方法必须不能省，不然不能通过json字符串解析成java对象
*/
public Student() {
}
public Student(int id, String name) {
this.id = id;
this.name = name;
}
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 class Teacher {
private int id;
private String name;
private List<Student> stus;
/**
* 默认的构造方法必须不能省，不然不能通过json字符串解析成java对象
*/
public Teacher() {
}
public Teacher(int id, String name) {
this.id = id;
this.name = name;
}
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 List<Student> getStus() {
return stus;
}
public void setStus(List<Student> stus) {
this.stus = stus;
}
public void addStudent(Student stu){
this.stus.add(stu);
}
public void addStudents(List<Student> stus){
for (Student stu : stus) {
this.stus.add(stu);
}
}
public void setStudents(List<Student> stus){
this.stus=stus;
}
}
public class JsonTest1 {
public static void main(String[] args) {
Student stu=new Student(1,"one");
//java实例转化成json字符串
String jsonStr=test1(stu);
print();
//json字符串转成java实例
stu=test2(jsonStr);
print();
//集合转成json字符串
jsonStr=test3();
print();
//复杂集合转成json字符串
test4();
print();
}
//java实例转化成json字符串
public static String test1(Student stu){
String jsonStr=JSON.toJSONString(stu);
System.out.println(jsonStr);
return jsonStr;
}
//json字符串转成java实例
public static Student test2(String jsonStr){
Student stu=JSON.parseObject(jsonStr,Student.class);
System.out.println("转换前json字符串："+jsonStr);
System.out.println("转换后：id="+stu.getId()+",name="+stu.getName());
return stu;
}
//集合转成json字符串
public static String test3(){
List<Student> list=new ArrayList<Student>();
for(int i=1;i<=3;i++){
list.add(new Student(i,"name "+i));
}
String jsonStr=JSON.toJSONString(list);
System.out.println(jsonStr);
return jsonStr;
}
//复杂集合转成json字符串
public static String test4(){
List<Teacher> teaList = new ArrayList<Teacher>();
long time = System.currentTimeMillis();
for(int i=0;i<10;i++) {
Teacher teacher = new Teacher(i, "Teacher " + i);
List<Student> stus = new ArrayList<Student>();
for(int j = 0 ;j<4;j++) {
Student s = new Student(j, "Student" + j);
stus.add(s);
}
teacher.setStudents(stus);
teaList.add(teacher);
}
//true表示按照json格式输出
String jsonStr = JSON.toJSONString(teaList,true);
System.out.println(jsonStr);
return jsonStr;
}
public static void print(){
System.out.println("....................................");
}
}
输出结果：
{"id":1,"name":"one"}
....................................
转换前json字符串：{"id":1,"name":"one"}
转换后：id=1,name=one
....................................
[{"id":1,"name":"name 1"},{"id":2,"name":"name 2"},{"id":3,"name":"name 3"}]
....................................
[
{
"id":0,
"name":"Teacher 0",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":1,
"name":"Teacher 1",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":2,
"name":"Teacher 2",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":3,
"name":"Teacher 3",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":4,
"name":"Teacher 4",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":5,
"name":"Teacher 5",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":6,
"name":"Teacher 6",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":7,
"name":"Teacher 7",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":8,
"name":"Teacher 8",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
},
{
"id":9,
"name":"Teacher 9",
"stus":[
{
"id":0,
"name":"Student0"
},
{
"id":1,
"name":"Student1"
},
{
"id":2,
"name":"Student2"
},
{
"id":3,
"name":"Student3"
}
]
}
]
....................................
如果对类中有些字段不解析，可以通过SimplePropertyPreFilter来选取需要需要解析的属性，例子如下：
//类中有个别字段不解析
public static void test5(){
Student stu=new Student(1,"one");
SimplePropertyPreFilter filter=new SimplePropertyPreFilter(Student.class,"id");
String jsonStr=JSON.toJSONString(stu,filter);
System.out.println(jsonStr);
}
输出结果：
{"id":1}
把list集合的json字符串反序列为list集合：
public static void test6(){
List<Student> students = new ArrayList<Student>();
for(int i=0;i<5;i++) {
Student stu = new Student(i, "Student" + i);
students.add(stu);
}
// 过滤哪些属性需要转换
// SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Student.class, "id","age");
// String jsonStu =JSON.toJSONString(students,filter);
String jsonStu =JSON.toJSONString(students);
System.out.println(jsonStu);
List<Student> stu =JSON.parseObject(jsonStu, new TypeReference<List<Student>>(){});
for(int i=0;i<stu.size();i++)
{
System.out.println(stu.get(i));
}
}
代码输出：
[{"id":0,"name":"Student0"},{"id":1,"name":"Student1"},{"id":2,"name":"Student2"},{"id":3,"name":"Student3"},{"id":4,"name":"Student4"}]
com.main.etl.server.json.Student@60682430
com.main.etl.server.json.Student@551ffcc2
com.main.etl.server.json.Student@270b5037
com.main.etl.server.json.Student@57bf5ee7
com.main.etl.server.json.Student@54efbcb2