第一版

package com.zh.oukele.util;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class CreateSqlUtil {

    public static void main(String[] args) {

        Map<String ,Object> map = new HashMap<>();
        map.put("stuName","欧可乐");
        map.put("stuAge",20);
        map.put("stuSex","男");
        map.put("Key_stuId","ASDF");
        map.put("Key_stuSex","ASDF");
        try {
            System.out.println(getSql("table_name", "delete", map, false, ""));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**
     * 动态组装 简单sql语法
     * @param tableName 表名
     * @param operation 操作标识符 select|delete|update ,默认为 select
     * @param mapData 数据的map集合
     * @param useMySQL true|false , false 为使用动态组装SQL，true为使用自已的sql
     * @param mySql 自已的sql
     * 注意：update 这里，where xxx = xxx ,的时候，mapData 里的键必须要有 Key_ 前缀（其他的 并不影响到）
     *
     * @return
     * @throws Exception
     */
    public static String getSql(String tableName, String operation, Map<?,?> mapData,boolean useMySQL,String mySql) throws Exception {
        String sql = null;
        // 使用组装sql的功能
        if( !useMySQL){
            if( !(tableName != null && !tableName.equals("") && tableName.length() > 0 ) ){
                throw new Exception(" 参数 tableName 的值为空！");
            }else if( !(mapData != null && !mapData.equals("") && mapData.size() > 0 ) ){
                throw new Exception(" 参数 mapData 的值为空！");
            }
            // 操作标识 默认为 select
            String operations = "select";
            String condition = " a.* from " + tableName + " a where ";
            if( operation != null && !operation.equals("") ){
                if( operation.equals("update") || operation.equals("UPDATE") ){
                    operations = "update";
                    condition = " " + tableName + " a set ";
                }else if( operation.equals("delete") || operation.equals("DELETE") ){
                    operations = "delete";
                    condition = " from " + tableName + " a where ";
                }else if( operation.equals("insert") || operation.equals("INSERT") ){
                    operations = "insert";
                    condition = " into " + tableName + " values (";
                    String link = "";
                    Iterator<?> iterator = mapData.keySet().iterator();
                    while (iterator.hasNext()) {
                        String next = (String) iterator.next();
                        condition += link + next;
                        link = ",";
                    }
                    condition += ") values( ";
                }
            }
            String value= "";
            String link ="";
            String keyValueOperations = " where ";
            Iterator<? extends Map.Entry<?, ?>> iterator = mapData.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry<?, ?> next = iterator.next();
                if( next.getValue() instanceof String ){
                    value = "'" + next.getValue() +"'";
                }else {
                    value = "" + next.getValue() +"";
                }
                if( next.getKey().toString().lastIndexOf("Key_") == -1 ){
                    if( !operations.equals("insert")){
                        if( operations.equals("select") || operations.equals("delete")){
                            condition += link + "a." + next.getKey();
                            condition += "=" + value;
                            link = " and ";
                        }else {
                            condition += link + "a." + next.getKey();
                            condition += "=" + value;
                            link = ",";
                        }
                    }else {
                        condition += link + value;
                        link = ",";
                    }
                }else {
                    continue;
                }
            }

            // 组装 insert sql 的结尾
            if( operations.equals("insert") ){
                condition += ")";
            }else if(operations.equals("update")){ // 组装 update sql 的结尾
                condition += " where ";
                String and = "";
                Iterator<? extends Map.Entry<?, ?>> iterator1 = mapData.entrySet().iterator();
                while (iterator1.hasNext()) {
                    Map.Entry<?, ?> next = iterator1.next();
                    if( next.getValue() instanceof String ){
                        value = "'" + next.getValue() +"'";
                    }else {
                        value = "" + next.getValue() +"";
                    }
                    String key = next.getKey().toString();
                    if( key.lastIndexOf("Key_") != -1 ){
                        key =  key.substring(key.indexOf("Key_")+ 4,key.length());
                       condition += and +"a." +key + "=" + value;
                       and = " and ";
                    }
                }
            }

            sql = operations + condition;
        }else { // 不使用组装sql的功能
            sql = mySql;
        }
        return sql;
    }
}