import java.io.Serializable;
import java.util.List;
import com.alibaba.fastjson.JSONObject;
//通過Serializable的toString方法，將類轉變為json字串
public class AwardPara implements Serializable {
 private String merchantId;
 private String sn;
 private String timestamp;
 private Body body;//內部類
 
 public String getMerchantId() {
  return merchantId;
 }
 public void setMerchantId(String merchantId) {
  this.merchantId = merchantId;
 }
 public String getSn() {
  return sn;
 }
 public void setSn(String sn) {
  this.sn = sn;
 }
 public String getTimestamp() {
  return timestamp;
 }
 public void setTimestamp(String timestamp) {
  this.timestamp = timestamp;
 }
 //注意內部類的set方法
 public Body getBody() {
  return body;
 }
 //內部類通過內部類的構造器和set方法進行賦值
 public void setBody(String issue,String lotoId) {
  this.body = new Body(issue,lotoId);
 }

 //外部引數通過構造器賦值
 public AwardPara(String merchantId, String sn,String timestamp) {
  this.merchantId = merchantId;
  this.sn = sn;
  this.timestamp = timestamp;
 }

 public static class Body implements Serializable {
  private String issue;
  private String lotoId;
  //內部類的構造器
  public Body (String issue,String lotoId){
   this.issue = issue;
   this.lotoId = lotoId;
  }
  public String getIssue() {
   return issue;
  }
  public void setIssue(String issue) {
   this.issue = issue;
  }
  public String getLotoId() {
   return lotoId;
  }
  public void setLotoId(String lotoId) {
   this.lotoId = lotoId;
  }
  
 }
 @Override
 public String toString() {
  return JSONObject.toJSONString(this);
 }
}

2、下面是如何呼叫該實體類並賦值

//實體類外部引數賦值
  AwardPara awardPara = new AwardPara(merchantId,"01201605311237390001","2017");
  //實體類的內部類賦值
  awardPara.setBody("2017077", "101");
  //將實體類轉換為json字串，
  String para = awardPara.toString();

3、得到的para的結果如下

{"body":{"issue":"2017077","lotoId":"101"},"merchantId":"0029","sn":"01201605311237390001","timestamp":"2017"}