Android中解析Json_fastJson
阿新 • • 發佈:2019-02-06
首先建立兩個實體類,Student.java 和 Teacher.java
Student.java 和Teacher.java 的程式碼如下:
[java] view plaincopyprint?- package com.android.fastjson.bean;
- publicclass Student {
- privateint id;
- private String name;
- privateint age;
- /**
- * 預設的構造方法必須不能省,不然不能解析
- */
- public Student(){
- }
- public Student(int id,String name,int age) {
- this.id = id;
- this.name = name;
- this.age = age;
- }
- publicint getId() {
- return id;
- }
- publicvoid setId(int id) {
- this.id = id;
- }
- public String getName() {
- return name;
- }
- publicvoid setName(String name) {
- this.name = name;
- }
- publicint getAge() {
- return age;
- }
- publicvoid setAge(int age) {
- this.age = age;
- }
- @Override
- public String toString() {
- return"Student [id=" + id + ", name=" + name + ", age="
- }
- }
package com.android.fastjson.bean;
public class Student {
private int id;
private String name;
private int age;
/**
* 預設的構造方法必須不能省,不然不能解析
*/
public Student(){
}
public Student(int id,String name,int age) {
this.id = id;
this.name = name;
this.age = age;
}
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
}
}
[java] view plaincopyprint?
- package com.android.fastjson.bean;
- import java.util.List;
- publicclass Teacher {
- privateint id;
- private String name;
- private List<Student> students;
- /**
- * 預設的構造方法必須不能省,不然不能解析
- */
- public Teacher() {
- }
- public Teacher(int id,String name) {
- this.id = id;
- this.name = name;
- }
- publicint getId() {
- return id;
- }
- publicvoid setId(int id) {
- this.id = id;
- }
- public String getName() {
- return name;
- }
- publicvoid setName(String name) {
- this.name = name;
- }
- public List<Student> getStudents() {
- return students;
- }
- publicvoid setStudents(List<Student> students) {
- this.students = students;
- }
- @Override
- public String toString() {
- return"Teacher [id=" + id + ", name=" + name + ", mStudents="
- + students + "]";
- }
- }
package com.android.fastjson.bean;
import java.util.List;
public class Teacher {
private int id;
private String name;
private List<Student> students;
/**
* 預設的構造方法必須不能省,不然不能解析
*/
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> getStudents() {
return students;
}
public void setStudents(List<Student> students) {
this.students = students;
}
@Override
public String toString() {
return "Teacher [id=" + id + ", name=" + name + ", mStudents="
+ students + "]";
}
}
上面 的程式碼比較簡單,主要就幾個屬性,這裡值得注意的是, 預設的建構函式一定要寫,不然是無法解析的。(對於fastjson 嚴格按照JavaBean的規範來,有一點不對就無法解析,這裡一定要切記,每一個實體類的屬性的get , set 方法必須寫,切方法第四個字母必須大寫,最好使用Eclipse的source->genreal setters and getters 生成get,set 方法,切記,切記 )。對於Gson 這裡就沒有這麼多的要求了,但最好還是按照JavaBean來寫,避免一些位置的錯誤。
上面主要基本的介紹完了,就開始解析,首先要下載fastjson 和Gson的jar包,這個網上很多請自行下載。
首先看 fastjson 的解析
首先解析一個實體類為json 格式。
[html] view plaincopyprint?- Student student = new Student(0, "Aaron", 24);
- System.out.println(JSON.toJSONString(student));
Student student = new Student(0, "Aaron", 24);
System.out.println(JSON.toJSONString(student));
[html]
view plaincopyprint?
- 輸出結果為:{"age":24,"id":0,"name":"Aaron"}
輸出結果為:{"age":24,"id":0,"name":"Aaron"}
輸出的json格式與我們的Student中定義的屬性其實是不一致的,這個其實不影響我們生成以及後面的解析,因為他有嚴格的get和set方法定義。
更復雜一點的資料型別也可以很方便的使用JSON.toJsonString(Object o) 這個方法進行解析成json格式。
[java] view plaincopyprint?- List<Student> students = new ArrayList<Student>();
- for(int i=0;i<5;i++) {
- Student stu = new Student(i, "Student" + i, 18 +i);
- students.add(stu);
- }
List<Student> students = new ArrayList<Student>();
for(int i=0;i<5;i++) {
Student stu = new Student(i, "Student" + i, 18 +i);
students.add(stu);
}
解析結果為:
[plain]
view plaincopyprint?
- [{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"},{"age":20,"id":2,"name":"Student2"},{"age":21,"id":3,"name":"Student3"},{"age":22,"id":4,"name":"Student4"}]
[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"},{"age":20,"id":2,"name":"Student2"},{"age":21,"id":3,"name":"Student3"},{"age":22,"id":4,"name":"Student4"}]
我們來看看更復雜一點的結構。 我們將一個Teacher 列表來解析,一個Teacher物件中是包含Student 列表的這個也在我們常用的資料模型,下面看看程式碼:
[java]
view plaincopyprint?
- 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, 18 +j);
- stus.add(s);
- }
- teacher.setStudents(stus);
- teaList.add(teacher);
- }
- String jsonTeach = JSON.toJSONString(teaList);
- System.out.println("fastjson = " + jsonTeach);
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, 18 +j);
stus.add(s);
}
teacher.setStudents(stus);
teaList.add(teacher);
}
String jsonTeach = JSON.toJSONString(teaList);
System.out.println("fastjson = " + jsonTeach);
結果為:
[plain] view plaincopyprint?- fastjson = [{"id":0,"name":"Teacher 0","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":1,"name":"Teacher 1","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":2,"name":"Teacher 2","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":3,"name":"Teacher 3","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]}]
fastjson = [{"id":0,"name":"Teacher 0","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":1,"name":"Teacher 1","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":2,"name":"Teacher 2","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]},{"id":3,"name":"Teacher 3","students":[{"age":18,"id":0,"name":"Student0"},{"age":19,"id":1,"name":"Student1"}]}]
[plain]
view plaincopyprint?
- 還是一個簡單的函式而已,就能辦到。
還是一個簡單的函式而已,就能辦到。
[plain]
view plaincopyprint?
- 這個還有toJSONString 過載的方法,有很多,在給一個就是可以按照標準的json 格式輸出,上面的輸出都不規範,我們來看看,
這個還有toJSONString 過載的方法,有很多,在給一個就是可以按照標準的json 格式輸出,上面的輸出都不規範,我們來看看,
[plain]
view plaincopyprint?
- Student student = new Student(0, "Aaron", 24);
- System.out.println(JSON.toJSONString(student,true));
- 輸出為:
- {
- "age":24,
- "id":0,
- "name":"Aaron"
- }
Student student = new Student(0, "Aaron", 24);
System.out.println(JSON.toJSONString(student,true));
輸出為:
{
"age":24,
"id":0,
"name":"Aaron"
}
如果我們想要將實體類中的某個欄位或某幾個不進行解析呢?那麼我們可以使用transient 關鍵字,來標記它為不需要的,在fastjson中還提供了一種便捷的方法來自定義我們需要序列化的欄位,
[java] view plaincopyprint?- SimplePropertyPreFilter filter = new SimplePropertyPreFilter(實體類.class, "欄位1","欄位2"); 欄位為我們需要序列化的欄位,如果實體類中沒有改欄位則不解析放棄該欄位而不會報錯。
SimplePropertyPreFilter filter = new SimplePropertyPreFilter(實體類.class, "欄位1","欄位2"); 欄位為我們需要序列化的欄位,如果實體類中沒有改欄位則不解析放棄該欄位而不會報錯。
如下:
[java] view plaincopyprint?- SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Student.class, "id","age");
- String jsonStu =JSON.toJSONString(students,filter);
SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Student.class, "id","age");
String jsonStu =JSON.toJSONString(students,filter);
這樣就只會序列化 id和age 的欄位。
下面進行fastjson 的反序列化,這個也是很常用的功能,
還是拿最簡單的來進行示範,
[java] view plaincopyprint?- Student student = new Student(0, "Aaron", 24);
- String str = JSON.toJSONString(student,true);
- System.out.println(JSON.parseObject(str,Student.class));
Student student = new Student(0, "Aaron", 24);
String str = JSON.toJSONString(student,true);
System.out.println(JSON.parseObject(str,Student.class));
反序列化主要使用的是JSON.parseObject(str,class); 它就能把我們的str 轉化為class 型別的物件,當然還有更復雜的物件,比如:
[java]
view plaincopyprint?
- List<Student> students = new ArrayList<Student>();
- for(int i=0;i<5;i++) {
- Student stu = new Student(i, "Student" + i, 18 +i);
- students.add(stu);
- }
- // 過濾哪些屬性需要轉換
- // 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));
- }
List<Student> students = new ArrayList<Student>();
for(int i=0;i<5;i++) {
Student stu = new Student(i, "Student" + i, 18 +i);
students.add(stu);
}
// 過濾哪些屬性需要轉換
// 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));
}
前面就是新增資料,然後在後面解析為json格式,然後在轉化為類的物件,這裡轉為List<Student> 物件,主要用到new TypeReference<資料返回型別> (){},我們使用的就是new TypeReference<List<Student>>(){} 返回的結果就是List<Student>也不需要強制轉化,我們看看上面輸出的結果為: [java] view plaincopyprint?
- Student [id=0, name=Student0, age=18]
- Student [id=1, name=Student1, age=19]
- Student [id=2, name=Student2, age=20]
- Student [id=3, name=Student3, age=21]
- Student [id=4, name=Student4, age=22]
Student [id=0, name=Student0, age=18]
Student [id=1, name=Student1, age=19]
Student [id=2, name=Student2, age=20]
Student [id=3, name=Student3, age=21]
Student [id=4, name=Student4, age=22]
當然fastjson 能處理的資料型別還有很多很多,我主要列了我常用的資料型別,今天主要就講到這裡。