我们做项目，通常会使用前后端分离的ajax交互，那么前后端交互的数据格式通常是json格式。这里既有牵扯到json和对象集合之间的转换，目前市面上的json转换主要有三种：
下面将会对这三种转换进行简单的入门演示：
工程名任意，打包方式选择jar
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.58</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.8.1</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.1</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>compile</scope>
</dependency>
</dependencies>
<build>
<plugins>
<!-- java编译插件 -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
public class Student implements Serializable {
private String sid;
private String name;
private Integer age;
private String address;
public Student() {
}
public Student(String sid, String name, Integer age, String address) {
this.sid = sid;
this.name = name;
this.age = age;
this.address = address;
}
public String getSid() {
return sid;
}
public void setSid(String sid) {
this.sid = sid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Student{" +
"sid='" + sid + '\'' +
", name='" + name + '\'' +
", age=" + age +
", address='" + address + '\'' +
'}';
}
}public class JackSonTest {
//对象和json字符串之间的转换
@Test
public void jsonAndJsonStr() throws IOException {
//创建学生的对象
Student student = new Student();
student.setSid("1001");
student.setName("张无忌");
student.setAge(18);
student.setAddress("冰火岛");
//创建jackson的转换对象
ObjectMapper om = new ObjectMapper();
//将对象转为json字符串
String studentStr = om.writeValueAsString(student);
System.out.println(studentStr);
//将json字符串转为对象
Student stu = om.readValue(studentStr, Student.class);
System.out.println("stu = " + stu);
}
//list集合和json字符串之间的转换
@Test
public void listAndJsonStr() throws IOException {
//创建list集合
List<Student> studentList = new ArrayList<>();
studentList.add(new Student("1001","刘德华",22,"香港"));
studentList.add(new Student("1002","张学友",21,"香港"));
studentList.add(new Student("1003","郭富城",18,"香港"));
studentList.add(new Student("1004","黎明",19,"香港"));
//创建jackson的转换对象
ObjectMapper om = new ObjectMapper();
String listStr = om.writeValueAsString(studentList);
System.out.println(listStr);
//json字符串转换为集合
List<Student> list = om.readValue(listStr, List.class);
System.out.println(list);
}
}public class FastJsonTest {
//对象和json字符串之间的转换
@Test
public void jsonAndJsonStr() throws IOException {
//创建学生的对象
Student student = new Student();
student.setSid("1001");
student.setName("张无忌");
student.setAge(18);
student.setAddress("冰火岛");
//创建fastjson的转换对象
JSONObject jsonObject = new JSONObject();
//将对象转换为json字符串
String studentStr = jsonObject.toJSONString(student);
System.out.println(studentStr);
//将json字符串解析为对象
Student stu = JSON.parseObject(studentStr, Student.class);
System.out.println(stu);
}
//list集合和json字符串之间的转换
@Test
public void listAndJsonStr() throws IOException {
//创建list集合
List<Student> studentList = new ArrayList<>();
studentList.add(new Student("1001","刘德华",22,"香港"));
studentList.add(new Student("1002","张学友",21,"香港"));
studentList.add(new Student("1003","郭富城",18,"香港"));
studentList.add(new Student("1004","黎明",19,"香港"));
//创建fastjson的转换对象
JSONObject jsonObject = new JSONObject();
//将集合转换为json字符串
String listStr = jsonObject.toJSONString(studentList);
System.out.println(listStr);
//将json字符串转换为集合
List<Student> list = JSON.parseArray(listStr, Student.class);
System.out.println(list);
}
}public class GsonTest {
//对象和json字符串之间的转换
@Test
public void jsonAndJsonStr() throws IOException {
//创建学生的对象
Student student = new Student();
student.setSid("1001");
student.setName("张无忌");
student.setAge(18);
student.setAddress("冰火岛");
//创建json转换对象
Gson gson = new Gson();
//将对象转换为json字符串
String studentStr = gson.toJson(student);
System.out.println(studentStr);
//将json字符串转换为对象
Student stu = gson.fromJson(studentStr, Student.class);
System.out.println(stu);
}
//list集合和json字符串之间的转换
@Test
public void listAndJsonStr() throws IOException {
//创建list集合
List<Student> studentList = new ArrayList<>();
studentList.add(new Student("1001","刘德华",22,"香港"));
studentList.add(new Student("1002","张学友",21,"香港"));
studentList.add(new Student("1003","郭富城",18,"香港"));
studentList.add(new Student("1004","黎明",19,"香港"));
//创建json转换对象
Gson gson = new Gson();
//将集合转换为json字符串
String listStr = gson.toJson(studentList);
System.out.println(listStr);
//将json字符串转换为集合
List<Student> list = gson.fromJson(listStr, List.class);
System.out.println(list);
}
}Gson性能最好，当不断增加的时候到了100000，Gson明细弱于Jackson和FastJson， 这时候FastJson性能是真的牛，另外还可以看到不管数量少还是多，Jackson一直表现优异。
数据量转换比较小时，建议使用Gson，其它情况考虑另外两种。
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