我有一个实体:
E{
String screen;
}
我需要将屏幕字段分配给我作为 json 字符串接收的值之一
"屏幕":{"ldpi":"1.jpg","mdpi":"2.jpg","hdpi":"3.jpg","xhdpi":"4.jpg"}
不幸的是,我不能声明容器类而不仅仅是字符串,因为 E 类被 orm 系统使用。
为了实现它,我创建了自定义值反序列化器:
public class DensityDeserializer extends JsonDeserializer<String> {
public final static int LDPI = 0;
public final static int MDPI = 1;
public final static int HDPI = 2;
public final static int XHDPI = 3;
private int mDensity = LDPI;
public DensityDeserializer() {
}
public DensityDeserializer(int density) {
mDensity = density;
}
@Override
public String deserialize(JsonParser jsonparser,
DeserializationContext deserializationcontext) throws IOException,
JsonProcessingException {
ScreenContainer screenContainer = jsonparser
.readValueAs(ScreenContainer.class);
switch (mDensity) {
default:
return "";
case LDPI:
return screenContainer.getLdpi();
case MDPI:
return screenContainer.getHdpi();
case HDPI:
return screenContainer.getHdpi();
case XHDPI:
return screenContainer.getXhdpi();
}
}
public static class ScreenContainer {
public String ldpi = "";
public String mdpi = "";
public String hdpi = "";
public String xhdpi = "";
public ScreenContainer() {
// TODO Auto-generated constructor stub
}
public String getLdpi() {
return ldpi;
}
public void setLdpi(String ldpi) {
this.ldpi = ldpi;
}
public String getMdpi() {
return mdpi;
}
public void setMdpi(String mdpi) {
this.mdpi = mdpi;
}
public String getHdpi() {
return hdpi;
}
public void setHdpi(String hdpi) {
this.hdpi = hdpi;
}
public String getXhdpi() {
return xhdpi;
}
public void setXhdpi(String xhdpi) {
this.xhdpi = xhdpi;
}
}
}
当我运行程序时,它会引发异常:
01-11 12:29:06.833: W/System.err(1501): com.fasterxml.jackson.databind.JsonMappingException: 无法从 JSON 字符串实例化类型 [简单类型,类 .DensityDeserializer$ScreenContainer] 的值;没有单字符串构造函数/工厂方法(通过引用链:E.["screen"])
有什么建议么 ?