alibaba/canal · error · NullPointerException
dbMapping.table
Error message
dbMapping.table
What it means
Thrown by rdb MappingConfig.validate() when dbMapping.table is null or empty AND mirrorDb is false. table is the source table name; for non-mirror mappings it is mandatory, but mirrorDb mappings (whole-schema sync) intentionally omit it, hence the getMirrorDb() guard.
Source
Thrown at client-adapter/rdb/src/main/java/com/alibaba/otter/canal/client/adapter/rdb/config/MappingConfig.java:87
public String getDestination() {
return destination;
}
public void setDestination(String destination) {
this.destination = destination;
}
public AdapterMapping getMapping() {
return dbMapping;
}
public void validate() {
if (dbMapping.database == null || dbMapping.database.isEmpty()) {
throw new NullPointerException("dbMapping.database");
}
if (!dbMapping.getMirrorDb() && (dbMapping.table == null || dbMapping.table.isEmpty())) {
throw new NullPointerException("dbMapping.table");
}
if (!dbMapping.getMirrorDb() && (dbMapping.targetTable == null || dbMapping.targetTable.isEmpty())) {
throw new NullPointerException("dbMapping.targetTable");
}
}
public static class DbMapping implements AdapterMapping {
private boolean mirrorDb = false; // 是否镜像库
private String database; // 数据库名或schema名
private String table; // 表名
private Map<String, String> targetPk = new LinkedHashMap<>(); // 目标表主键字段
private boolean mapAll = false; // 映射所有字段
private String targetDb; // 目标库名
private String targetTable; // 目标表名
private Map<String, String> targetColumns; // 目标表字段映射
private boolean caseInsensitive = false; // 目标表不区分大小写，默认是否View on GitHub (pinned to 87be50e876)
Solutions
- For a table mapping, add a non-empty 'table:' under dbMapping.
- If this is a whole-schema mirror, set 'mirrorDb: true' under dbMapping so table/targetTable are not required.
Example fix
# table mapping fix # before dbMapping: database: mytest # after dbMapping: database: mytest table: user # mirror-db alternative dbMapping: mirrorDb: true database: mytest
Defensive patterns
Strategy: validation
Validate before calling
DbMapping m = config.getDbMapping();
boolean needsTable = m == null || !m.getMirrorDb();
if (needsTable && (m.getTable() == null || m.getTable().isEmpty())) {
throw new IllegalArgumentException(
"rdb yml missing dbMapping.table for " + fileName
+ " (or set mirrorDb:true for whole-schema sync)");
} Prevention
- For table mappings always set table; for whole-schema mirrors set mirrorDb:true instead.
- Validate the mirrorDb/table combination in CI.
When it happens
Trigger: A non-mirror rdb mapping yml's dbMapping block omits or blanks 'table:', or mirrorDb is false/unset on a config that was meant to be a mirror.
Common situations: A table-mapping template had 'table:' deleted. A mirror-schema config forgot 'mirrorDb: true' so the validator still demands a table.
Related errors
AI-assisted analysis of alibaba/canal@87be50e876 (2026-08-14).
Data as JSON: /api/errors/b0e95f1b73d3d992.
Report an issue: GitHub.