废话少说,直接上代码

package com.sx.utils.mysql;

import com.sun.istack.internal.NotNull;
import com.sx.utils.StringUtils;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by Administrator on 2018/2/27 0027.
 */
public class GenerateEntityMysql {
    private String url;// 数据库链接地址
    private String username;// 用户名
    private String password;//密码
    private String tablename;//表名
    private String databasename;// 数据库名
    private String packagename;// 欲生成的实体类的包名
    private String entityname;// 欲生成的实体类的名称
    private String path;// 生成的实体类的文件夹路径

    private Map<String, String> map = new HashMap<>();

    public GenerateEntityMysql(
            @NotNull String url,//
            @NotNull String username,//
            @NotNull String password, //
            @NotNull String tablename, //
            @NotNull String databasename,//
            @NotNull String packagename, //
            @NotNull String entityname,//
            @NotNull String path) {
        this.url = url;
        this.username = username;
        this.password = password;
        this.tablename = tablename;
        this.databasename = databasename;
        this.packagename = packagename;
        this.entityname = entityname;
        this.path = path;
    }

    public void generate() {
        // 查询欲生成实体类的表的详细信息
        String sql = "SELECT information_schema.`COLUMNS`.* FROM information_schema.`COLUMNS` WHERE information_schema.`COLUMNS`.TABLE_SCHEMA=? AND information_schema.`COLUMNS`.TABLE_NAME=?";
        try {
            Connection conn;
            PreparedStatement ps = null;
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, username, password);
            System.out.println("connect database success...");
            ps = conn.prepareStatement(sql);
            ps.setString(1, databasename);
            ps.setString(2, tablename);
            ResultSet rs = ps.executeQuery();
            StringBuilder sb = new StringBuilder();
            sb.append("package ");
            sb.append(packagename);
            sb.append(";\n");
            sb.append("public class ");
            sb.append(entityname);
            sb.append("{\n");
            // 生成成员变量
            while (rs.next()) {
                String column_name = rs.getString("COLUMN_NAME");
                column_name = StringUtils.underline2Camel(column_name.toLowerCase(), true);
                String data_type = rs.getString("DATA_TYPE");
                String column_comment = rs.getString("COLUMN_COMMENT");
                sb.append("\tprivate ");
                if (data_type.equalsIgnoreCase("TINYINT")) {
                    sb.append("Boolean ");
                    map.put(column_name, "Boolean");
                } else if (data_type.equalsIgnoreCase("SMALLINT") ||
                        data_type.equalsIgnoreCase("MEDIUMINT") ||
                        data_type.equalsIgnoreCase("INT") ||
                        data_type.equalsIgnoreCase("INTEGER")) {
                    sb.append("Integer ");
                    map.put(column_name, "Integer");
                } else if (data_type.equalsIgnoreCase("BIGINT")) {
                    sb.append("Long ");
                    map.put(column_name, "Long");
                } else if (data_type.equalsIgnoreCase("FLOAT") ||
                        data_type.equalsIgnoreCase("DOUBLE")) {
                    sb.append("Double ");
                    map.put(column_name, "Double");
                } else if (data_type.equalsIgnoreCase("DECIMAL")) {
                    sb.append("Decimal ");
                    map.put(column_name, "Decimal");
                } else if (data_type.equalsIgnoreCase("DATE") ||
                        data_type.equalsIgnoreCase("TIME") ||
                        data_type.equalsIgnoreCase("YEAR") ||
                        data_type.equalsIgnoreCase("DATETIME") ||
                        data_type.equalsIgnoreCase("TIMESTAMP")) {
                    sb.append("Date ");
                    map.put(column_name, "Date");
                } else {
                    sb.append("String ");
                    map.put(column_name, "String");
                }
                sb.append(column_name).append("; // ").append(column_comment).append("\n");
            }
            sb.append("\n");
            // 生成get|set方法
            processAllMethod(sb);
            sb.append("}");
            //FileOutputStream fos = new FileOutputStream();
            // 打印文件
            File file = new File(("/".equals(path.substring(path.length()-1))?path:(path+"/")) + entityname + ".java");
            if (!file.exists()) {
                file.createNewFile();
            } else {
                file.delete();
                file.createNewFile();
            }
            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
            bw.write(sb.toString());
            bw.flush();
            bw.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 生成get,set
     *
     * @param sb
     */
    private void processAllMethod(StringBuilder sb) {
        // 遍历map,此为java8遍历
        map.forEach((k, v) -> {
            // 键值首字母大写
            String m = k.substring(0, 1).toUpperCase() + k.substring(1);
            // 生成set
            sb//
                    .append("\tpublic void set")//
                    .append(m)//
                    .append("(")//
                    .append(v)//
                    .append(" ")//
                    .append(k)//
                    .append("){\n")//
                    .append("\t\tthis.")//
                    .append(k)//
                    .append(" = ")//
                    .append(k)//
                    .append(";\n")//
                    .append("\t}\n\n");//
            // 生成get
            sb//
                    .append("\tpublic ")//
                    .append(v)//
                    .append(" get")//
                    .append(m)//
                    .append("(){\n")//
                    .append("\t\treturn ")//
                    .append(k)//
                    .append(";\n")//
                    .append("\t}\n\n");//
        });
    }

    public static void main(String[] args) {
        new GenerateEntityMysql(
                "jdbc:mysql://*.*.*.*/sxfp?characterEncoding=utf8&useSSL=false",
                "****",
                "****",
                "****",
                "****",
                "****",
                "****",
                "E:/"
        ).generate();
    }
}

package com.sx.utils;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by Administrator on 2018/2/27 0027.
 */
public class StringUtils {
    /**
     * 下划线转驼峰法
     * @param line 源字符串
     * @param smallCamel 大小驼峰,是否为小驼峰
     * @return 转换后的字符串
     */
    public static String underline2Camel(String line,boolean smallCamel){
        if(line==null||"".equals(line)){
            return "";
        }
        StringBuffer sb=new StringBuffer();
        Pattern pattern= Pattern.compile("([A-Za-z\\d]+)(_)?");
        Matcher matcher=pattern.matcher(line);
        while(matcher.find()){
            String word=matcher.group();
            sb.append(smallCamel&&matcher.start()==0?Character.toLowerCase(word.charAt(0)):Character.toUpperCase(word.charAt(0)));
            int index=word.lastIndexOf('_');
            if(index>0){
                sb.append(word.substring(1, index).toLowerCase());
            }else{
                sb.append(word.substring(1).toLowerCase());
            }
        }
        return sb.toString();
    }
    /**
     * 驼峰法转下划线
     * @param line 源字符串
     * @return 转换后的字符串
     */
    public static String camel2Underline(String line){
        if(line==null||"".equals(line)){
            return "";
        }
        line=String.valueOf(line.charAt(0)).toUpperCase().concat(line.substring(1));
        StringBuffer sb=new StringBuffer();
        Pattern pattern=Pattern.compile("[A-Z]([a-z\\d]+)?");
        Matcher matcher=pattern.matcher(line);
        while(matcher.find()){
            String word=matcher.group();
            sb.append(word.toUpperCase());
            sb.append(matcher.end()==line.length()?"":"_");
        }
        return sb.toString();
    }
}