ELK系列(4) - Elasticsearch cannot write xcontent for unknown value of type class java.math.BigDecimal

問題與分析

在使用Elasticsearch進行index數據時，發現報錯以下：

java.lang.IllegalArgumentException: cannot write xcontent for unknown value of type class java.math.BigDecimal
	at org.elasticsearch.common.xcontent.XContentBuilder.unknownValue(XContentBuilder.java:755)
	at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:726)
	at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:711)
	at org.elasticsearch.index.query.BaseTermQueryBuilder.doXContent(BaseTermQueryBuilder.java:154)
	at org.elasticsearch.index.query.AbstractQueryBuilder.toXContent(AbstractQueryBuilder.java:82)
	at org.elasticsearch.index.query.BoolQueryBuilder.doXArrayContent(BoolQueryBuilder.java:275)
	at org.elasticsearch.index.query.BoolQueryBuilder.doXContent(BoolQueryBuilder.java:256)
	at org.elasticsearch.index.query.AbstractQueryBuilder.toXContent(AbstractQueryBuilder.java:82)
	at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:779)
	at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:772)
	at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:764)
	at org.elasticsearch.search.builder.SearchSourceBuilder.toXContent(SearchSourceBuilder.java:1184)
	at org.elasticsearch.common.xcontent.XContentHelper.toXContent(XContentHelper.java:349)
	at org.elasticsearch.search.builder.SearchSourceBuilder.toString(SearchSourceBuilder.java:1558)
	at org.elasticsearch.search.builder.SearchSourceBuilder.toString(SearchSourceBuilder.java:1553)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at org.elasticsearch.action.search.SearchRequest.toString(SearchRequest.java:516)

從異常信息看，顯然ES沒法接受BigDecimal類型，通過百度，也確實如此。在一篇博文評論中解釋以下：

應該是客戶端代碼裏將查詢的數值定義成了java.math.BigDecimal，而ES不支持這個類型。之因此2.2沒有問題，是由於以前的transport client發送數據以前將其序列化成了json，而在5.x之後，使用的內部的transport protocol，數據類型若是不匹配會拋錯誤。

因此數據類型的定義上，須要使用ES支持的類型。

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解決方案

方案一：轉變成其餘ES支持的數據類型

我使用的是6.4.2版本的Elasticsearch，該版本尚不支持BigDecimal或者BigInteger的數據類型，因此在index到Elasticsearch以前，須要轉換成其餘數據類型，這裏要注意不要數據溢出了:

1. BigDecimal要轉變成Double類型
2. BigInteger要轉變成Long類型

方案二：使用更高版本的ES

我在看6.7.1版本的Elasticsearch源碼時發現已經能夠支持BigDecimal或者BigInteger的數據類型了，因此直接使用該版本或更高版本的就好了。

下面附上兩個版本的支持的數據類型的源碼：

• 6.4.2版本的Elasticsearch相關源碼

Map<Class<?>, Writer> writers = new HashMap<>();
writers.put(Boolean.class, (b, v) -> b.value((Boolean) v));
writers.put(Byte.class, (b, v) -> b.value((Byte) v));
writers.put(byte[].class, (b, v) -> b.value((byte[]) v));
writers.put(Date.class, XContentBuilder::timeValue);
writers.put(Double.class, (b, v) -> b.value((Double) v));
writers.put(double[].class, (b, v) -> b.values((double[]) v));
writers.put(Float.class, (b, v) -> b.value((Float) v));
writers.put(float[].class, (b, v) -> b.values((float[]) v));
writers.put(Integer.class, (b, v) -> b.value((Integer) v));
writers.put(int[].class, (b, v) -> b.values((int[]) v));
writers.put(Long.class, (b, v) -> b.value((Long) v));
writers.put(long[].class, (b, v) -> b.values((long[]) v));
writers.put(Short.class, (b, v) -> b.value((Short) v));
writers.put(short[].class, (b, v) -> b.values((short[]) v));
writers.put(String.class, (b, v) -> b.value((String) v));
writers.put(String[].class, (b, v) -> b.values((String[]) v));
writers.put(Locale.class, (b, v) -> b.value(v.toString()));
writers.put(Class.class, (b, v) -> b.value(v.toString()));
writers.put(ZonedDateTime.class, (b, v) -> b.value(v.toString()));
writers.put(Calendar.class, XContentBuilder::timeValue);
writers.put(GregorianCalendar.class, XContentBuilder::timeValue);

• 6.7.1版本的Elasticsearch相關源碼

Map<Class<?>, Writer> writers = new HashMap<>();
writers.put(Boolean.class, (b, v) -> b.value((Boolean) v));
writers.put(Byte.class, (b, v) -> b.value((Byte) v));
writers.put(byte[].class, (b, v) -> b.value((byte[]) v));
writers.put(Date.class, XContentBuilder::timeValue);
writers.put(Double.class, (b, v) -> b.value((Double) v));
writers.put(double[].class, (b, v) -> b.values((double[]) v));
writers.put(Float.class, (b, v) -> b.value((Float) v));
writers.put(float[].class, (b, v) -> b.values((float[]) v));
writers.put(Integer.class, (b, v) -> b.value((Integer) v));
writers.put(int[].class, (b, v) -> b.values((int[]) v));
writers.put(Long.class, (b, v) -> b.value((Long) v));
writers.put(long[].class, (b, v) -> b.values((long[]) v));
writers.put(Short.class, (b, v) -> b.value((Short) v));
writers.put(short[].class, (b, v) -> b.values((short[]) v));
writers.put(String.class, (b, v) -> b.value((String) v));
writers.put(String[].class, (b, v) -> b.values((String[]) v));
writers.put(Locale.class, (b, v) -> b.value(v.toString()));
writers.put(Class.class, (b, v) -> b.value(v.toString()));
writers.put(ZonedDateTime.class, (b, v) -> b.value(v.toString()));
writers.put(Calendar.class, XContentBuilder::timeValue);
writers.put(GregorianCalendar.class, XContentBuilder::timeValue);
writers.put(BigInteger.class, (b, v) -> b.value((BigInteger) v));
writers.put(BigDecimal.class, (b, v) -> b.value((BigDecimal) v));

能夠發現，在6.7.1版本的源碼裏，多出了最後的兩種數據類型的支持：BigInteger和BigDecimal。

參考連接

• elastic search 5.4.版本，java api 調用出現：can not write type [class java.math.BigDecimal]