Why Lombok’s Getter/Setter Breaks MyBatis and EasyExcel: Hidden Pitfalls Explained

Preface

Last year we introduced the Lombok plugin, which eliminated boilerplate such as getters, setters, and toString, but we later discovered hidden pitfalls that affect other components.

Setter‑Getter Pitfall

Problem Discovery

Using Lombok’s @Data (which generates setter/getter methods) we encountered a MyBatis insert where the enum field nMetaType was always persisted as null.

Entity example:

@Data
public class NMetaVerify {
    private NMetaType nMetaType;
    private Long id;
    // ... other fields
}

All other fields were inserted correctly, but nMetaType remained null in the database.

Root Cause

Lombok generates getter/setter names that differ from the JavaBeans convention when the first letter is lowercase and the second letter is uppercase. MyBatis uses reflection to locate getter/setter methods, expecting the standard naming, so it fails to find the correct accessor.

Generated by Lombok:

public void setNMetaType(NMetaType nMetaType) { ... }
public NMetaType getNMetaType() { ... }

Standard JavaBeans (used by MyBatis, IDEs, and the JDK):

public NMetaType getnMetaType() { ... }
public void setnMetaType(NMetaType nMetaType) { ... }

MyBatis’s PropertyNamer.methodToProperty logic shows how it derives property names from method prefixes and handles the case where the second character is uppercase.

String methodToProperty(String name) {
    // ... logic that lower‑cases the first character unless the second is uppercase
}

A test confirms the conversion results:

Method name: isName   Property name: name
Method name: getName  Property name: name
Method name: getnMetaType   Property name: nMetaType
Method name: getNMetaType   Property name: NMetaType

@Accessor(chain = true) Issue

Problem Discovery

When exporting data with EasyExcel, newly added entities annotated with @Accessor(chain = true) failed to map correctly.

We use chainable setters like:

new UserDto()
    .setUserName("")
    .setAge(10)
    .setBirthday(new Date());

Root Cause

EasyExcel relies on CGLIB’s BeanMap, which in turn uses the JDK’s Introspector. The introspector only recognizes setter methods that return void. The chained setters generated by Lombok return the object itself, so they are ignored, leading to missing property values.

Solution

Remove the @Accessor(chain = true) annotation from the entity.

Alternatively, wait for EasyExcel to switch to a reflection library that supports non‑void setters.