[QUESTION]使用parseObject反序列化一个类,类中包含一个枚举类,会出现null的情况,请问该怎么解决这个问题?

[formatsystem]

请描述您的问题

询问有关本项目的使用和其他方面的相关问题。

public class JsonClass {
    private String name;

    private EnumClass enumClass;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public EnumClass getEnumClass() {
        return enumClass;
    }

    public void setEnumClass(EnumClass enumClass) {
        this.enumClass = enumClass;
    }
}

public enum EnumClass {
    NONE, ONE, TWO;


    public String toValue() {
        switch (this) {
            case NONE:
                return "none";
            case ONE:
                return "one";
            case TWO:
                return "two";
            default:
                return "none";
        }
    }

    public EnumClass forValue(String value) {
        switch (value) {
            case "one":
                return ONE;
            case "two":
                return TWO;
            case "none":
                return NONE;
            default:
                return NONE;
        }
    }
}

    public void testParseObject(){
        String json = "{\"name\":\"hello\",\"enumClass\":\"\"}";

        JsonClass jsonClass = JSON.parseObject(json, JsonClass.class);
        System.out.println("--------> "+jsonClass.getEnumClass());
    }

结果如图

[wenshao]

空字符串会当做空值处理

[formatsystem]

空字符串会当做空值处理

我想问,如果出现null,能否指定一个初始值?该如何指定?避免后续方法出现问题

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.47-SNAPSHOT/
更新到2.0.47-SNAPSHOT版本，可以如下这样用，看下是否符合你的需求

    @Test
    public void test() {
        assertEquals(Type.NONE, JSON.parseObject("{}", Bean.class).type);
        assertEquals(Type.NONE, JSON.parseObject("{\"type\":null}", Bean.class).type);
        assertEquals(Type.NONE, JSON.parseObject("{\"type\":\"\"}", Bean.class).type);
    }

    public static class Bean {
        @JSONField(defaultValue = "NONE")
        public Type type;
    }

    public enum Type {
        NONE, ONE, TWO
    }

[formatsystem]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.47-SNAPSHOT/ 更新到2.0.47-SNAPSHOT版本，可以如下这样用，看下是否符合你的需求

    @Test
    public void test() {
        assertEquals(Type.NONE, JSON.parseObject("{}", Bean.class).type);
        assertEquals(Type.NONE, JSON.parseObject("{\"type\":null}", Bean.class).type);
        assertEquals(Type.NONE, JSON.parseObject("{\"type\":\"\"}", Bean.class).type);
    }

    public static class Bean {
        @JSONField(defaultValue = "NONE")
        public Type type;
    }

    public enum Type {
        NONE, ONE, TWO
    }

能达到需求,但需要将属性从private改成public才可以.
上方您给出的代码如果将type改成priavte 并生成对应的 get set方法执行后就会出现如下错误.

test方法中仅保留
Assert.assertEquals(Type.NONE, JSON.parseObject("{"type":""}", Bean.class).getType());

执行后就提示如下

com.alibaba.fastjson2.JSONException: illegal defaultValue : NONE, class com.gf.fastjson2.FastJson2Test$Type

at com.alibaba.fastjson2.reader.ObjectReaderCreator.createFieldReaderMethod(ObjectReaderCreator.java:2107)
at com.alibaba.fastjson2.reader.ObjectReaderCreator.createFieldReader(ObjectReaderCreator.java:1547)
at com.alibaba.fastjson2.reader.ObjectReaderCreator.lambda$createFieldReaders$4(ObjectReaderCreator.java:1654)
at com.alibaba.fastjson2.util.BeanUtils.setters(BeanUtils.java:573)
at com.alibaba.fastjson2.reader.ObjectReaderCreator.createFieldReaders(ObjectReaderCreator.java:1650)
at com.alibaba.fastjson2.reader.ObjectReaderCreatorASM.createObjectReader(ObjectReaderCreatorASM.java:259)
at com.alibaba.fastjson2.reader.ObjectReaderProvider.getObjectReaderInternal(ObjectReaderProvider.java:854)
at com.alibaba.fastjson2.reader.ObjectReaderProvider.getObjectReader(ObjectReaderProvider.java:746)
at com.alibaba.fastjson2.JSON.parseObject(JSON.java:780)
at com.gf.fastjson2.FastJson2Test.test(FastJson2Test.java:793)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.47-SNAPSHOT/
帮忙更新快照版本2.0.47-SNAPSHOT，问题已经修复，帮忙再验证下是否还有问题

[formatsystem]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.47-SNAPSHOT/ 帮忙更新快照版本2.0.47-SNAPSHOT，问题已经修复，帮忙再验证下是否还有问题

问题已解决!

[wenshao]

https://github.com/alibaba/fastjson2/releases/tag/2.0.47
请用新版本