基于freemarker自动生成mapper多条件查询语句

1,创建mapper.xml 模板文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--${tableconment}mapper -->
<mapper namespace="${tablename}mapper">

    <!--查询${tableconment}列表 -->
    <select id="selectlist" parameterType="java.util.HashMap"
            resultType="java.util.HashMap">
        select
        <#list tableColumnList as tablecolumn>
            <#if  tablecolumn_index= tableColumnList?size-1>
                <!--  ${tablecolumn.columncomment}   -->
                a.${tablecolumn.columnname?lower_case}
            <#else >
                <!--  ${tablecolumn.columncomment}   -->
                a.${tablecolumn.columnname?lower_case},
            </#if>
        </#list>
        from
        ${tableschema}.${tablename} as a
        <#if veanddepquanxian?? && veanddepquanxian=true>
            left join vehicle v on a.vehicleId =v.vehicleId and v.deleted=false
        </#if>

        <#if depquanxian??  &&depquanxian=true>
            left join department d on a.depId =d.depId and d.deleted=false
        </#if>
        where 1=1
        <#list tableColumnList as tablecolumn>
            <#if tablecolumn.datatype=="int" && tablecolumn.columnname?lower_case !="deleted">
                <if test="${tablecolumn.columnname?lower_case} != null ">
                    and a.${tablecolumn.columnname?lower_case}=${r"#"}{${tablecolumn.columnname?lower_case}}
                </if>
            </#if>
            <#if  tablecolumn.columnname?lower_case =="deleted">
                and a.deleted=false
            </#if>
            <#if tablecolumn.datatype=="varchar">
                <if test="${tablecolumn.columnname?lower_case} != null ">
                    and a.${tablecolumn.columnname?lower_case}=${r"#"}{${tablecolumn.columnname?lower_case}}
                    <!-- and a.${tablecolumn.columnname?lower_case} like '%${r"$"}{${tablecolumn.columnname?lower_case}}%'-->
                </if>
            </#if>
            <#if tablecolumn.datatype=="datetime">
                <if test="start${tablecolumn.columnname?lower_case} != null ">
                    and a.${tablecolumn.columnname?lower_case} >= ${r"#"}{start${tablecolumn.columnname?lower_case} }
                </if>
                <if test="end${tablecolumn.columnname?lower_case} != null ">
                    and <![CDATA[ a.${tablecolumn.columnname?lower_case} < ${r"#"}{end${tablecolumn.columnname?lower_case} }]]>
                </if>
            </#if>
        </#list>

      
        <#if ordercol??>
            order by a.${ordercol} desc
        </#if>

    </select>


</mapper>

2,查询数据库获取对应表的字段,主键,类型,注释等

  String sql = "select table_schema tableschema,table_name tablename,\n" +
                "column_name columnname,column_key columnkey,data_type datatype,column_comment columncomment  from\n" +
                "information_schema.COLUMNS where table_schema =? and table_name=? ";
@Data
public class TableColumn {

    private String tableschema;
    private String tablename;
    private String columnname;//字段名
    private String columnkey; //主键,外键等
    private String datatype; //字段类型
    private String columncomment;//字段注释

}
//获取表注释
    public TableNameVo searchTableName(String table_schema, String table_name) {
        String sql = " select table_name tablename,table_comment tableconment from INFORMATION_SCHEMA.TABLES  where table_schema = ?\n" +
                "AND table_name =?";
        TableNameVo tableNameVo = mysqlDao.queryFirst(sql, TableNameVo.class, table_schema, table_name);
        return tableNameVo;
    }
@Data
public class TableNameVo {
private String tablename;
private String tableconment;
}

3,查询出来表的内容之后

  //模板内容的类
  
public class TableVo {

    private String pricolname;//主键名称
    private String tableschema;//所在数据库
    private String tablename;//表名
    private String packpath;//class所在package位置
    private String classname;//自定义的class名称

    private PackageVo packageVo;//各个类所在的package位置
    private String entityName;//大写的类名
    private String tableconment;//表注释

    private String ordercol;//排序字段

    private List<TableColumn> tableColumnList;//字段内容

上面是用来写入ftl的数据,可以*想象加入更多数据

4,根据模板文件生成对应文件,这里可以是html也可以是任意文件

 /**
     * //写入模板
     * @param ftlpath 模板路径
     * @param classpath 要写入的文件路径
     * @param tableVo 查出来的表的内容,字段名,表名注释等
     */
    private void writetem(String ftlpath, String classpath, TableVo tableVo) {
        Writer out = null;
        // step4 加载模版文件
        try {
            Template template = configuration.getTemplate(ftlpath);
            // step5 生成数据
            File docFile = new File(classpath);
            out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(docFile)));
            // step6 输出文件
            template.process(tableVo, out);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (TemplateException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != out) {
                    out.flush();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }

    }