• 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

     

     

     

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  • 原文地址:https://www.cnblogs.com/yangh2016/p/5732201.html
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