/** * 用于字段更新的注解 * * @author user */ @Retention(RetentionPolicy.RUNTIME) public @interface TableUpdateField { } @Slf4j public class UpdateSqlProvider { /** * 缓存构建好后的SQL表达式，相同的实体类对应的SQL表达式是不变的 * 比如UPDATE `test` `name` = #{name}, `age` = #{age}, WHERE `ID` = #{id}; */ public static final Map SQL_MAP_CACHE = new ConcurrentHashMap<>(); /** * SimpleBaseMapper的method的入口 * * @param obj 数据库实体类 * @return SQL */ public static String build(final TableEntity obj) { // 使用class全限定类名作为key保证唯一 Class clazz = obj.getClass(); String tableName = getTableName(obj); String key = clazz.getName() + "#" + tableName; // 双重检查锁定，同一个实体类只需要生成一次 String sql = SQL_MAP_CACHE.get(key); if (sql == null) { synchronized (clazz) { sql = SQL_MAP_CACHE.get(key); if (sql == null) { // 初始化SQL sql = initSql(key, obj); SQL_MAP_CACHE.put(key, sql); log.debug("InsertSqlProvider init sql for: {}. sql: {}", key, sql); } } } return sql; } /** * 从TableEntity获取表名 * * @param obj 实体类对象 * @return 表名 */ private static String getTableName(TableEntity obj) { return obj.getTableName(); } /** * 初始化实体类的Sql * * @param obj 数据库实体类 * @param key * @return SQL */ private static String initSql(String key, TableEntity obj) { String tableName = getTableName(obj); StringJoiner setClause = new StringJoiner(" "); StringJoiner whereClause = new StringJoiner(" AND "); Field[] fields = obj.getClass().getDeclaredFields(); for (Field field : fields) { String fieldName = field.getName(); String columnName = null; // set的语句构建 TableField tableFieldAnnotation = field.getAnnotation(TableField.class); if (tableFieldAnnotation != null && tableFieldAnnotation.exist()) { columnName = tableFieldAnnotation.value(); setClause.add(" `" + columnName + "` = #{" + fieldName + "}, "); } // where的语句构建，字段上需要注解TableUpdateFiled，这个注解是新增的 if (field.isAnnotationPresent(TableUpdateField.class)) { if (columnName == null) { TableId annotation = field.getAnnotation(TableId.class); columnName = annotation.value(); } if (columnName == null) { throw new IllegalArgumentException("Class " + key + "Field " + fieldName + " @TableUpdateField use illegal, At least @TableField or @TableId annotation is required."); } whereClause.add("`" + columnName + "` = #{" + fieldName + "}"); } } // 防止全局更新，这里判断一下whereClause是否有字段 if (whereClause.length() == 0) { throw new IllegalArgumentException("Class " + key + " does not have any TableUpdateField annotated Field."); } return String.format("", tableName, setClause, whereClause); } }