扩展BaseMapper类 - 详解

扩展mybatis-plus的BaseMapper类

• insertBatch
• insertIfNotExists

mp的BaseMapper只提供了简单的增删改查方法，一些复杂点的操作没有提供，或是在IService类中提供。如果想要直接通过mapper类调用这些方法，可以通过扩展BaseMapper来使其获取新的功能。

insertBatch

扩展一个批量插入insertBatch的方法。

1. 定义SqlInjector类，扩展功能

public class ExpandSqlInjector extends DefaultSqlInjector {
@Override
public List<AbstractMethod> getMethodList(Class<?> mapperClass) {List<AbstractMethod> methodList = super.getMethodList(mapperClass);methodList.add(new InsertBatchMethod());methodList.add(new InsertIfNotExistsMethod());return methodList;}/*** 批量插入方法*/public static class InsertBatchMethod extends AbstractMethod {@Overridepublic MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?> modelClass, TableInfo tableInfo) {String sql = "<script>INSERT INTO %s (%s) VALUES %s";List<String> columnList = new ArrayList<>();List<String> propertyList = new ArrayList<>();if (tableInfo.havePK() && !AUTO.equals(tableInfo.getIdType())) {columnList.add(tableInfo.getKeyColumn());propertyList.add(tableInfo.getKeyProperty());}// getFiledList等方法获取的内容会自动根据@TableField相关配置而改变for (TableFieldInfo fieldInfo : tableInfo.getFieldList()) {columnList.add(fieldInfo.getColumn());propertyList.add(fieldInfo.getProperty());}String columns = String.join(",", columnList);String values = "<foreach collection='list' item='item' separator=','>" +"(#{item." + String.join("},#{item.", propertyList) + "})" +"</foreach></script>";String sqlResult = String.format(sql, tableInfo.getTableName(), columns, values);SqlSource sqlSource = languageDriver.createSqlSource(configuration, sqlResult, modelClass);return getMappedStatement(this::addInsertMappedStatement, mapperClass, "insertBatch", modelClass, tableInfo, sqlSource, "");}}private static MappedStatement getMappedStatement(MappedStatementMethod method, Class<?> mapperClass, String id, Class<?> modelClass, TableInfo tableInfo, SqlSource sqlSource, String prefix) {// 根据@TableId注解自动设置KeyGeneratorKeyGenerator keyGenerator = NoKeyGenerator.INSTANCE; // 默认值String keyColumn = null;String keyProperty = null;// 如果表有主键字段if (tableInfo.havePK()) {keyColumn = tableInfo.getKeyColumn();keyProperty = prefix + tableInfo.getKeyProperty();// 根据主键类型设置，INPUT、NONE：NoKeyGenerator，ASSIGN_ID, ASSIGN_UUID等策略，Java层面生成，不需要数据库生成if (AUTO.equals(tableInfo.getIdType())) {keyGenerator = Jdbc3KeyGenerator.INSTANCE;}}// 这里的keyGenerator与实际sql语句无关，是否插入id取决你构造的sql语句return method.accept(mapperClass, modelClass, id, sqlSource, keyGenerator, keyProperty, keyColumn);}@FunctionalInterfacepublic interface MappedStatementMethod {MappedStatement accept(Class<?> mapperClass, Class<?> parameterType, String id, SqlSource sqlSource, KeyGenerator keyGenerator, String keyProperty, String keyColumn);}}

2. 配置SqlInjector：在mp的配置类中（也可以通过yml文件配置）

@Bean
public ExpandSqlInjector expandSqlInjector() {
return new ExpandSqlInjector();
}

3. 具体mapper类加上insertBatch方法；或定义一个新的BaseMapper，让其继承BaseMapper（推荐后者，可以统一配置）

实际通过前面二步，生成的BaseMapper代理类已经有了扩展的方法，这一步了是为了让接口也拥有扩展方法。

public interface AppMapper<T> extends BaseMapper<T> {/*** 批量插入* @param list 实体列表* @return 插入条数*/int insertBatch(List<T> list);}

insertIfNotExists

扩展一个不存在则插入insertIfNotExists的方法。

1. ExpandSqlInjector类中添加以下内容

/**
* 如果满足条件的记录不存在才插入
*/
public static class InsertIfNotExistsMethod extends AbstractMethod {
@Override
public MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?> modelClass, TableInfo tableInfo) {// 动态生成 SQLString sql = "<script>INSERT INTO %s (%s) " +"SELECT %s FROM dual " +"WHERE NOT EXISTS (" +"   SELECT 1 FROM %s ${ew.customSqlSegment}" +")</script>";// 1. 插入的字段列表（会自动加上if标签，根据类型添加相关的非空判断，最后一个字段会多个逗号）String insertColumns = tableInfo.getAllInsertSqlColumnMaybeIf("entity.");insertColumns = SqlScriptUtils.convertTrim(insertColumns, null, null, null, ",");// 2. 插入的值（会自动加上if标签，根据类型添加相关的非空判断，最后一个值会多个逗号）String insertValues = tableInfo.getAllInsertSqlPropertyMaybeIf("entity.");insertValues = SqlScriptUtils.convertTrim(insertValues, null, null, null, ",");String tableName = tableInfo.getTableName();String sqlResult = String.format(sql, tableName, insertColumns, insertValues, tableName);SqlSource sqlSource = languageDriver.createSqlSource(configuration, sqlResult, modelClass);return getMappedStatement(this::addInsertMappedStatement, mapperClass, "insertIfNotExists", modelClass, tableInfo, sqlSource, "entity.");}}

2. AppMapper类里添加以下内容：

/**
* 插入，如果满足指定条件的记录已存在则忽略
* @param entity 插入的实体类实例
* @param ew 条件对象
*/
int insertIfNotExists(@Param("entity") T entity, @Param(WRAPPER) Wrapper<T> ew);