How to map MyBatis database fields to Java enumeration

This article focuses on "how to map Java enumerations in MyBatis database fields". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let the editor take you to learn how MyBatis database fields map Java enumerations.

Sometimes we need to map the fields of the database to the enumeration types of Java. For example, we have an enumeration of auto parts types.

Public enum ProductType implements Localisable {TYPE1 ("accessories"), TYPE2 ("car products"); private String value; private ProductType (String value) {this.value = value;} @ Override public String getValue () {return this.value;}}

This enumeration type implements an interface

Public interface Localisable {String getValue ();}

An entity class with a fitting category that contains the enumerated field (here only some field properties are included)

/ * AllArgsConstructor@NoArgsConstructorpublic class ProviderProductLevel {@ Getter @ Setter private Long id; @ Getter @ Setter private String code; @ Setter private String name; @ Getter @ Setter private Integer sort; @ Setter private Integer level; @ Getter @ Setter private ProductType productType; @ Getter @ Setter private String pictureUrl;}

The table structure in the database is as follows

The dao method is as follows (find a fitting category through id and instantiate it)

@ Mapperpublic interface LevelDao {ProviderProductLevel findLevel1 (Long id);}

The mapper mapping file is as follows

Select id,code,name,sort,product_type from product_level id=# {id}

We can see that there is a mapping processor typeHandler= "com.cloud.productprovider.untils.DbEnumTypeHandler" here.

The code for the mapping processor is as follows

@ AllArgsConstructorpublic class DbEnumTypeHandler extends BaseTypeHandler {private Class type; @ Override public void setNonNullParameter (PreparedStatement ps, int I, Localisable parameter, JdbcType jdbcType) throws SQLException {ps.setString (iParameter.getValue ());} @ Override public Localisable getNullableResult (ResultSet rs, String columnName) throws SQLException {String value = rs.getString (columnName); if (rs.wasNull ()) {return null;} else {return convert (value) } @ Override public Localisable getNullableResult (ResultSet rs, int columnIndex) throws SQLException {String value = rs.getString (columnIndex); if (rs.wasNull ()) {return null;} else {return convert (value);} @ Override public Localisable getNullableResult (CallableStatement cs, int columnIndex) throws SQLException {String value = cs.getString (columnIndex); if (cs.wasNull ()) {return null } else {return convert (value);}} private Localisable convert (String value) {Localisable [] dbEnums = type.getEnumConstants (); for (Localisable dbEnum: dbEnums) {if (dbEnum.getValue (). Equals (value)) {return dbEnum;}} return null;}}

The Json string of the result object returned by the test is as follows

{"code": "0000001", "id": 1, "name": "Oil products", "productType": "TYPE1", "sort": 1}

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