java对象和json的相互转换--（1） 使用@JsonSerialize对javabean进行json格式化

java对象和json的相互转换--（1） 使用@JsonSerialize对javabean进行json格式化
https://blog.csdn.net/wslyk606/article/details/80301782

以json格式输出数据是常用的方式，这次记录下项目中使用的json格式化方法，

使用的jar包为com.fasterxml.jackson.core:jackson-databind,对应的maven依赖为      

 <dependency>

            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.6.2</version>

        </dependency>

1 首先定义一个Student类

public class Student {
    private String name;
    private int age;
    private int number;
 
    public String getName() {
        return name;
    }
 
    public int getAge() {
        return age;
    }
 
    public int getNumber() {
        return number;
    }
 
    public Student(String name, int age, int number) {
 
        this.name = name;
        this.age = age;
        this.number = number;
    }
}

2 定义一个要格式化的类 StudentsReport，使用@JsonSerialize进行格式化，对应的格式化类为 StudentsReportSerializer

import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 
 
import java.util.List;
 
import static com.google.common.collect.Lists.newArrayList;
 
@JsonSerialize(using = StudentsReportSerializer.class)
public class StudentsReport {
    List<String> names = newArrayList();
    List<Student> studentList = newArrayList();
 
    public List<String> getNames() {
        return names;
    }
 
    public List<Student> getStudentList() {
        return studentList;
    }
 
    public StudentsReport(List<String> names, List<Student> studentList) {
 
        this.names = names;
        this.studentList = studentList;
    }
}

3  对应的格式化的类为

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
 
import java.io.IOException;
 
public class StudentsReportSerializer extends JsonSerializer <StudentsReport>{
@Override
    public void serialize(StudentsReport studentsReport, JsonGenerator jgen, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
        jgen.writeStartObject(); //start write :"{"
 
        jgen.writeFieldName("studentsName");
        jgen.writeStartArray();// write "["
        for (String name:studentsReport.getNames()
             ) {
            jgen.writeObject(name);
        }
        jgen.writeEndArray();
 
 
        jgen.writeFieldName("studentsData");
        jgen.writeStartArray();
        for (Student student : studentsReport.getStudentList()){
            jgen.writeStartObject();
 
            jgen.writeStringField("name",student.getName());
            jgen.writeNumberField("age",16);
            jgen.writeNumberField("number",1);
 
            jgen.writeEndObject();
        }
        jgen.writeEndArray();
 
        jgen.writeEndObject();  //end :"}"
    }
 
}

 4 进行测试

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
 
import java.util.List;
 
import static com.google.common.collect.Lists.newArrayList;
 
public class TestJson {
    public static void main(String[] args) throws JsonProcessingException {
        Student student1 = new Student("Tom",16,1);
        Student student2 = new Student("Jerry",17,2);
        List<Student> studentList = newArrayList();
        studentList.add(student1);
        studentList.add(student2);
 
        List<String> studentsName = newArrayList(student1.getName(),student2.getName());
 
 
 
        StudentsReport report = new StudentsReport(studentsName,studentList);
 
        ObjectMapper mapper = new ObjectMapper();
 
        String jsonReport = mapper.writeValueAsString(report);
 
        System.out.println(jsonReport);
 
    }
}

输出结果为   {"studentsName":["Tom","Jerry"],"studentsData":[{"name":"Tom","age":16,"number":1},{"name":"Jerry","age":16,"number":1}]}

即 ：{
    "studentsName":[
        "Tom",
        "Jerry"
    ],
    "studentsData":[
        {
            "name":"Tom",
            "age":16,
            "number":1
        },
        {
            "name":"Jerry",
            "age":16,
            "number":1
        }
    ]
}

ps：使用的newArrayList()是使用了com.google.guava这个包，对应的maven依赖为

        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>12.0.1</version>
        </dependency>