Java 反射由实体类生产hive或mysql表对应字段

最新推荐文章于 2024-04-29 19:48:45 发布

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最新推荐文章于 2024-04-29 19:48:45 发布

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分类专栏： Java Hive 文章标签： java反射 hive

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本文介绍如何利用Java反射特性，通过创建接口、枚举类和生成表类，简化RDBMS表的创建过程，减少手动编写重复代码的工作量。

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如果一个实体类字段特别多，那么创建对应的RDBMS对应的表会让我感到抓狂，可以利用Java反射特性，生产对应字段
1.创建一个借口，定义一些常量

public interface Constants {

    /**参数默认值*/
    public static final String DEFAULT_PARAM_VAL = "";
    /**中文字符集*/
    public static final String CHAR_UTF8 = "utf-8";
    /**数据默认分隔符*/
    public static final String DEFAULT_SEPAREATOR = "|";
    /**字段默认分隔符*/
    public static final String DEFAULT_FIELDS_SEPAREATOR = ",";
    /**空格字符串*/
    public static final String BLANK_SPACE = " ";
    /**换行字符*/
    public static final String LINE_FEED = "\n";
    /**制表符字符*/
    public static final String TAB = "\t";

}

2.创建一个枚举类，定义一些常用语句（可以根据，你自己的需求定义）

/**
 * 
 * @author puppy
 * @data 2015-04-02
 *
 */
public enum HiveTableSyntax {

    external("CREATE EXTERNAL TABLE ","external"),inner("CREATE TABLE ","inner"),
    defalut("PARTITIONED BY(logdate String) ROW FORMAT DELIMITED FIELDS TERMINATED BY '|' ","default"),
    sequence("PARTITIONED BY(logdate String) ROW FORMAT DELIMITED FIELDS TERMINATED BY '|' STORED AS SequenceFile ","sequence");

    private String value;
    private String index;

    private HiveTableSyntax() {
    }
    private HiveTableSyntax(String value) {
        this.value=value;
    }
    private HiveTableSyntax(String value,String index)  
    {  
        this.value=value;
        this.index=index;
    }  
    public static String getValue(String index){
        for(HiveTableSyntax hts:HiveTableSyntax.values()){
            if(hts.getIndex().equalsIgnoreCase(index)){
                return hts.getValue();
            }
        }
        return null;
    }
    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public String getIndex() {
        return index;
    }

    public void setIndex(String index) {
        this.index = index;
    }


}

3.创建生成表的类（我这里只写了生成hive表，对应其他请自己定义）

/**
 * 
 * @author puppy
 * @date 2015-04-01
 *
 */
public class AutoCreateFields {
    // 生成字段
    public static String create(Class<?> clazz) {

        Field[] fs = clazz.getDeclaredFields();
        Class<?> superClazz = clazz.getSuperclass();
        if (superClazz != null) {
            Field[] superFs = superClazz.getDeclaredFields();
            fs = (Field[]) ArrayUtils.addAll(fs, superFs);
        }
        StringBuffer sb = new StringBuffer();
        sb.append(Constants.LINE_FEED);
        sb.append("(");
        int size = fs.length;
        for (int i = 0; i < size; i++) {

            Field field = fs[i];
            field.setAccessible(true);
            sb.append(field.getName());
            sb.append(Constants.BLANK_SPACE);
            sb.append(field.getType().getSimpleName().equalsIgnoreCase("Integer")?"int":field.getType().getSimpleName());
            if (i + 1 != size) {

                sb.append(Constants.DEFAULT_FIELDS_SEPAREATOR);
                sb.append(Constants.LINE_FEED);
            }
        }
        sb.append(")");
        sb.append(Constants.LINE_FEED);
        return sb.toString();
    }
    //生成hive表
    public static String createHiveTable(Class<?> clazz,String tblname,String externalOrInner,String storeTpye){
        StringBuilder sb=new StringBuilder();
        String fields=create(clazz);
        String create=HiveTableSyntax.getValue(externalOrInner);
        String st=HiveTableSyntax.getValue(storeTpye);
        sb.append(create);
        sb.append(tblname);
        sb.append(fields);
        sb.append(st);
        return sb.toString();
    }
    public static void main(String[] args) {
        String result="Need Params:aqy or partner or v1 or default";

        if(args.length>0&&StringUtils.isNotBlank(args[0])){
            String value=args[0];

            switch (value){
            case "aqy":
                result=createHiveTable(AQYLogOriginal.class,"qiyi_log_original","external","sequence");
                break;
            case "partner":
                result=createHiveTable(PartnerLogOriginal.class,"partner_log_original","external","sequence");
                break;
            case "v1":
                result=createHiveTable(V1VodLogOriginal.class,"v1_log_original","external","sequence");
                break;
                default:
                result=createHiveTable(V1VodLogOriginal.class,"v0v1_log_original","external","sequence");   
                break;
            }

        }
        //String aqy = createHiveTable(AQYLogOriginal.class,"qiyi_log_original","external","sequence");
        //String partner = createHiveTable(PartnerLogOriginal.class,"partner_log_original","external","sequence");
        //String v1 = createHiveTable(V1VodLogOriginal.class,"v0v1_log_original","inner","sequence");
        System.out.println(result);
    }