8 fastJson的使用
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：
1 public class Student { 2 private int id; 3 4 private String name; 5 6 /** 7 * 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 8 */ 9 public Student() { 10 } 11 12 public Student(int id, String name) { 13 this.id = id; 14 this.name = name; 15 } 16 17 public int getId() { 18 return id; 19 } 20 21 public void setId(int id) { 22 this.id = id; 23 } 24 25 public String getName() { 26 return name; 27 } 28 29 public void setName(String name) { 30 this.name = name; 31 } 32 }
1 public class Teacher { 2 private int id; 3 4 private String name; 5 6 private List<Student> stus; 7 /** 8 * 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 9 */ 10 public Teacher() { 11 } 12 13 public Teacher(int id, String name) { 14 this.id = id; 15 this.name = name; 16 } 17 18 public int getId() { 19 return id; 20 } 21 22 public void setId(int id) { 23 this.id = id; 24 } 25 26 public String getName() { 27 return name; 28 } 29 30 public void setName(String name) { 31 this.name = name; 32 } 33 34 public List<Student> getStus() { 35 return stus; 36 } 37 38 public void setStus(List<Student> stus) { 39 this.stus = stus; 40 } 41 42 public void addStudent(Student stu){ 43 this.stus.add(stu); 44 } 45 46 public void addStudents(List<Student> stus){ 47 for (Student stu : stus) { 48 this.stus.add(stu); 49 } 50 } 51 52 public void setStudents(List<Student> stus){ 53 this.stus=stus; 54 } 55 }
1 public class JsonTest1 { 2 public static void main(String[] args) { 3 Student stu=new Student(1,"one"); 4 //java实例转化成json字符串 5 String jsonStr=test1(stu); 6 print(); 7 //json字符串转成java实例 8 stu=test2(jsonStr); 9 print(); 10 //集合转成json字符串 11 jsonStr=test3(); 12 print(); 13 14 //复杂集合转成json字符串 15 test4(); 16 print(); 17 18 19 20 } 21 //java实例转化成json字符串 22 public static String test1(Student stu){ 23 String jsonStr=JSON.toJSONString(stu); 24 System.out.println(jsonStr); 25 return jsonStr; 26 } 27 28 //json字符串转成java实例 29 public static Student test2(String jsonStr){ 30 Student stu=JSON.parseObject(jsonStr,Student.class); 31 System.out.println("转换前json字符串："+jsonStr); 32 System.out.println("转换后：id="+stu.getId()+",name="+stu.getName()); 33 return stu; 34 } 35 36 //集合转成json字符串 37 public static String test3(){ 38 List<Student> list=new ArrayList<Student>(); 39 for(int i=1;i<=3;i++){ 40 list.add(new Student(i,"name "+i)); 41 } 42 String jsonStr=JSON.toJSONString(list); 43 System.out.println(jsonStr); 44 return jsonStr; 45 } 46 47 //复杂集合转成json字符串 48 public static String test4(){ 49 List<Teacher> teaList = new ArrayList<Teacher>(); 50 long time = System.currentTimeMillis(); 51 for(int i=0;i<10;i++) { 52 Teacher teacher = new Teacher(i, "Teacher " + i); 53 List<Student> stus = new ArrayList<Student>(); 54 for(int j = 0 ;j<4;j++) { 55 Student s = new Student(j, "Student" + j); 56 stus.add(s); 57 } 58 teacher.setStudents(stus); 59 teaList.add(teacher); 60 } 61 //true表示按照json格式输出 62 String jsonStr = JSON.toJSONString(teaList,true); 63 System.out.println(jsonStr); 64 return jsonStr; 65 } 66 public static void print(){ 67 System.out.println("...................................."); 68 } 69 }
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：
1 //类中有个别字段不解析 2 public static void test5(){ 3 Student stu=new Student(1,"one"); 4 SimplePropertyPreFilter filter=new SimplePropertyPreFilter(Student.class,"id"); 5 String jsonStr=JSON.toJSONString(stu,filter); 6 System.out.println(jsonStr); 7 }
输出结果：
{"id":1}
把list集合的json字符串反序列为list集合：
1 public static void test6(){ 2 List<Student> students = new ArrayList<Student>(); 3 for(int i=0;i<5;i++) { 4 Student stu = new Student(i, "Student" + i); 5 students.add(stu); 6 } 7 // 过滤哪些属性需要转换 8 // SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Student.class, "id","age"); 9 // String jsonStu =JSON.toJSONString(students,filter); 10 String jsonStu =JSON.toJSONString(students); 11 System.out.println(jsonStu); 12 13 List<Student> stu =JSON.parseObject(jsonStu, new TypeReference<List<Student>>(){}); 14 for(int i=0;i<stu.size();i++) 15 { 16 System.out.println(stu.get(i)); 17 } 18 }
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
本文来自博客园，作者：life_start，转载请注明原文链接：https://www.cnblogs.com/yangh2016/p/5732201.html
