mybatis/mybatis-3 · error · BuilderException

Wrong namespace. Expected '{currentNamespace}' but found '{c

Error message

Wrong namespace. Expected '{currentNamespace}' but found '{currentNamespace}'.

What it means

setCurrentNamespace() enforces that one MapperBuilderAssistant instance (one mapper resource) is bound to exactly one namespace. If a different namespace string arrives after the first was set - nested <mapper> definitions, multiple root elements, or parser reuse across files - MyBatis throws this BuilderException showing expected vs found.

Source

Thrown at src/main/java/org/apache/ibatis/builder/MapperBuilderAssistant.java:81

  private boolean unresolvedCacheRef; // issue #676

  public MapperBuilderAssistant(Configuration configuration, String resource) {
    super(configuration);
    ErrorContext.instance().resource(resource);
    this.resource = resource;
  }

  public String getCurrentNamespace() {
    return currentNamespace;
  }

  public void setCurrentNamespace(String currentNamespace) {
    if (currentNamespace == null) {
      throw new BuilderException("The mapper element requires a namespace attribute to be specified.");
    }

    if (this.currentNamespace != null && !this.currentNamespace.equals(currentNamespace)) {
      throw new BuilderException(
          "Wrong namespace. Expected '" + this.currentNamespace + "' but found '" + currentNamespace + "'.");
    }

    this.currentNamespace = currentNamespace;
  }

  public String applyCurrentNamespace(String base, boolean isReference) {
    if (base == null) {
      return null;
    }
    if (isReference) {
      // is it qualified with any namespace yet?
      if (base.contains(".")) {
        return base;
      }
    } else {
      // is it qualified with this namespace yet?
      if (base.startsWith(currentNamespace + ".")) {

View on GitHub (pinned to 008069adb1)

Solutions

1. Inspect the mapper XML named in the error context: ensure exactly one root <mapper> with one namespace attribute
2. Split statements belonging to different namespaces into separate files, one namespace per file
3. If generating XML, ensure each emitted file has a single root element and a fixed namespace

Example fix

<!-- before (one file, two roots after bad merge) -->
<mapper namespace="com.example.A">...</mapper>
<mapper namespace="com.example.B">...</mapper>
<!-- after -->
<!-- file A.xml -->
<mapper namespace="com.example.A">...</mapper>
<!-- file B.xml -->
<mapper namespace="com.example.B">...</mapper>

// CI check: each mapper file has exactly one root <mapper> element and one namespace
// DocumentBuilderFactory is namespace-aware; reject files with >1 <mapper> root child

When it happens

Trigger: An XML file containing statements that applyCurrentNamespace resolves to a second namespace, e.g. cross-file references during incomplete parsing; an embedded mapper element inside another mapper file; tools that reuse the same assistant for multiple mapper files; XML structure issues (duplicated root elements after a bad merge).

Common situations: Bad merges leaving two <mapper> roots in one file; code generators emitting nested mapper elements; custom XML parsing pipelines reusing builder assistants.

Related errors

• The mapper element requires a namespace attribute to be spec
• Error resolving JdbcType. Cause: {cause}
• Error resolving ResultSetType. Cause: {cause}
• Error resolving ParameterMode. Cause: {cause}
• Error creating instance. Cause: {cause}

AI-assisted analysis of mybatis/mybatis-3@008069adb1 (2026-08-14). Data as JSON: /api/errors/e0f3b6f70670ca44. Report an issue: GitHub.