alibaba/canal · error · NullPointerException

dbMapping.targetTable

Error message

dbMapping.targetTable

What it means

Thrown as NullPointerException by MappingConfig.validate when, for a non-mirrorDb config, dbMapping.targetTable is null or empty. targetTable is the destination ClickHouse table name; required for non-mirrorDb configs. mirrorDb configs are exempt because they derive target tables automatically.

Source

Thrown at client-adapter/clickhouse/src/main/java/com/alibaba/otter/canal/client/adapter/clickhouse/config/MappingConfig.java:92

    }

    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

        private String              etlCondition;                            // etl条件sql

View on GitHub (pinned to 87be50e876)

Solutions

1. Set dbMapping.targetTable to the destination ClickHouse table name (even if identical to table).
2. For whole-DB mirroring, set dbMapping.mirrorDb: true to bypass the requirement.
3. Verify YAML indentation and restart the adapter.

Example fix

# before:
dbMapping:
  database: shop
  table: orders
# after:
dbMapping:
  database: shop
  table: orders
  targetTable: orders

MappingConfig.DbMapping m = config.getDbMapping();
if (!m.getMirrorDb() && (m.getTargetTable() == null || m.getTargetTable().isEmpty())) {
    throw new IllegalArgumentException("dbMapping.targetTable is required for non-mirrorDb config (file: " + fileName + ")");
}

When it happens

Trigger: A non-mirror mapping yml omitting targetTable; targetTable set to empty; intending source and target names to be equal but leaving the field blank (it is not auto-defaulted from table).

Common situations: Configuring a sync where the target ClickHouse table name was assumed to default to the source table name (it does not); template with blank targetTable; YAML indentation error.

Related errors

• dbMapping.database
• dbMapping.table
• ERROR Config: {} {}
• No clickhouse adapter found for config key: {}
• not allow to change outAdapterKey

AI-assisted analysis of alibaba/canal@87be50e876 (2026-08-14). Data as JSON: /api/errors/58facff5a57c0ace. Report an issue: GitHub.