[Java知识库]scala类转换为json

一，依赖

 <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <fastjson.version>1.2.54</fastjson.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>${fastjson.version}</version>
        </dependency>
    </dependencies>

二，java实例

public class JavaUser {
    private String userName;
    private String userSex;
    private int id;

    public JavaUser(String userName,String userSex,int id){
        this.userName=userName;
        this.userSex=userSex;
        this.id=id;
    }

    public String getUserName() {
        return userName;
    }

    public String getUserSex() {
        return userSex;
    }
}

import com.alibaba.fastjson.*;

public class JavaTest {
    public static void main(String[] args) {
        System.out.println(JSON.toJSONString(new JavaUser("zhangsan","man",1)));
    }
}

没有定义getter的字段，不会输出到json中。（public 修饰的字段可以）

 private int id;

三，scala实例

import scala.beans.BeanProperty

class ScalaUser(@BeanProperty val userName:String,@BeanProperty val userSex:String,_id:Int) {
  val id:Int=_id
}

import com.alibaba.fastjson.JSON

object ScalaTest {
  def main(args: Array[String]): Unit = {
    println(JSON.toJSONString(new ScalaUser("lisi", "woman",2),JSON.DEFAULT_GENERATE_FEATURE))

  }
}

使用@BeanProperty修饰的类成员会输出到json中。

四，原因

Scala中代码
var类型字段=private变量+getter+setter；
val类型字段=private变量+getter；
但是命名方式与java不同，getter为字段名，setter为**字段名_()**的形式，与fastjson要求的命名方式不一致。BeanProperty则能提供java风格的getter和setter。

package scala.beans

/** When attached to a field, this annotation adds a setter and a getter
 *  method following the Java Bean convention. For example:
 *  {{{
 *    @BeanProperty
 *    var status = ""
 *  }}}
 *  adds the following methods to the class:
 *  {{{
 *    def setStatus(s: String) { this.status = s }
 *    def getStatus: String = this.status
 *  }}}
 *  For fields of type `Boolean`, if you need a getter named `isStatus`,
 *  use the `scala.beans.BooleanBeanProperty` annotation instead.
 */
@scala.annotation.meta.field
class BeanProperty extends scala.annotation.StaticAnnotation