用java类实现动态SQL语句

在ContactMapper中

 @SelectProvider(type = useSql.class, method = "findContactByPage2")
    List<Contact> findContactByPage2(@Param("start") int start, @Param("pageSize") int pageSize,
                                     @Param("name") String name, @Param("max") String max, @Param("min") String min);

    @SelectProvider(type = useSql.class,method = "findTotalCount2")
    int findTotalCount2(@Param("name") String name, @Param("max") String max, @Param("min") String min);

useSql.java

public class useSql {
    public String findContactByPage2(@Param("start") int start, @Param("pageSize") int pageSize,@Param("name") String name, @Param("max") String max, @Param("min")String min) {
        String sql = "select * from contact where 1=1 ";
        if (name != null && name.trim().length() > 0) {
            sql += "and name like concat('%',#{name},'%')";
        }
        if (max != null && max.trim().length() > 0) {
            sql += " and age<#{max}";
        }
        if (min != null && min.trim().length() > 0) {
            sql += " and age>#{min}";
        }
        sql += "limit #{start},#{pageSize}";

        return sql;
    }

    public String findTotalCount2(@Param("name") String name, @Param("max") String max, @Param("min") String min) {
        String sql = "select count(*) from contact where 1=1 ";
        if (name != null && name.trim().length() > 0) {
            sql += " and name like concat('%',#{name},'%')";
        }
        if (max != null && max.trim().length() > 0) {
            sql += " and age<#{max}";
        }
        if (min != null && min.trim().length() > 0) {
            sql += " and age>#{min}";
        }

        return sql;
    }
}