JAVA高级面试进阶训练营视频教程

admin

我使用的net.sf.json是json-lib-2.4-jdk15.jar,把json对象转换为普通java实体对象时候有个问题，josn对象转换为java对象之后，json串里面的那几个小数点的值对应的java属性的值取不到。

json串如下所示:

{"Average":0.28,"Maximum":0.32,"Minimum":0.2,"instanceId":"i-426auf2hf","timestamp":1449938400000,"userId":"1467232540347717"}

java实体对象如下:

public class Model {
    private double Average;
    private double Maximum;
    private double Minimum;
    private String instanceId;
    private long timestamp;
    private String userId;

    public double getAverage() {
        return Average;
    }

    public void setAverage(double average) {
        Average = average;
    }

    public double getMaximum() {
        return Maximum;
    }

    public void setMaximum(double maximum) {
        Maximum = maximum;
    }

    public double getMinimum() {
        return Minimum;
    }

    public void setMinimum(double minimum) {
        Minimum = minimum;
    }

    public String getInstanceId() {
        return instanceId;
    }

    public void setInstanceId(String instanceId) {
        this.instanceId = instanceId;
    }

    public long getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(long timestamp) {
        this.timestamp = timestamp;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }
}

转换代码如下:

JSONObject sfObject = JSONObject.fromObject(str);
// 转换方法
Model ecs = (Model) JSONObject.toBean(sfObject, Model.class);
System.out.println(ecs.getAverage());

Average的值拿不到，所以输出的结果是:0.0,而不是0.28。

解决方案:

我放弃了json.lib,用google的Gson能够完美的解决。

Gson把json串转换成java实体对象的方法如下：

1.首页导入Gson的jar包，网上可以下载。

2. 实体类还是使用上面的实体类，转换代码如下所示:

String str = "{\"Average\":0.29,\"Maximum\":0.32,\"Minimum\":0.25,\"instanceId\":\"i-426auf2hf\",\"timestamp\":1449939900000,\"userId\":\"1467232540347717\"}";
Model model = new Gson().fromJson(str, Model.class);
System.out.println(model.getAverage());

使用Gson之后，打印结果正确。