[BUG] 复杂的嵌套bean，使用filter且map为null时将引发NPE

[timnick-snow]

问题描述

嵌套bean，使用filter，比如ValueFilter，当bean中有map且其值为null时，序列化将引发NPE

环境信息

请填写以下信息：

• OS信息： win11，win7，centos7
• JDK信息： jdk8，openjdk-17.0.2
• 版本信息：Fastjson2 2.0.4

重现步骤

public class CommonTest {

    @Getter
    @Setter
    public class DemoDto {
        private String var1;
        private Map<String, Object> var2;
    }

    @Test
    public void fun() throws Exception {
        DemoDto d0 = new DemoDto();
        d0.setVar1("d0");

        List<DemoDto> list = new ArrayList<>();
        list.add(d0);

        ValueFilter demoFilter = (object, name, value) -> value;
        System.out.println(JSON.toJSONString(list, demoFilter));
    }
}

期待的正确结果

正确序列化，输出json
该代码在fastjson1中正常运行

相关日志输出

java.lang.NullPointerException: Cannot invoke "java.util.Map.entrySet()" because "map" is null

	at com.alibaba.fastjson2.writer.ObjectWriterImplMap.writeWithFilter(ObjectWriterImplMap.java:402)
	at com.alibaba.fastjson2.writer.ObjectWriter.writeWithFilter(ObjectWriter.java:121)
	at com.alibaba.fastjson2.writer.ObjectWriterImplMap.write(ObjectWriterImplMap.java:322)
	at com.alibaba.fastjson2.writer.ObjectWriterAdapter.writeWithFilter(ObjectWriterAdapter.java:399)
	at com.alibaba.fastjson2.writer.ObjectWriter_1.write(Unknown Source)
	at com.alibaba.fastjson2.writer.ObjectWriterImplList.write(ObjectWriterImplList.java:254)
	at com.alibaba.fastjson2.JSON.toJSONString(JSON.java:980)

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson/2.0.5-SNAPSHOT/
这个兼容问题已经修复，你可以用2.0.5-SNAPSHOT验证，预计本周内会发布2.0.5版本

[wenshao]

https://github.com/alibaba/fastjson2/releases/tag/2.0.5
问题已修复，请用新版本