使用Java代码通过io流生成实体类

  前言：

        实体类在我们的项目中起着在至关重要的作用，所以实体类的编写也是必不可少的。大量的且重复的代码浪费我们很多的没有必要浪费时间。所以为了提高我们的工作效率，为此写了一个自动生成实体类的工具类。希望对大家有所帮助(￣▽￣)／

先调用里面的DatabaseInit()方法，之后再调用createEntity()方法。

createEntity()方法会创建连接的数据库中所有的表的实体类。

调用示例：

public static void main(String[] args) {
        String url="jdbc:mysql://localhost:3306/ruoy?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8";

        GenEntity.DatabaseInit(url,"root","123.","com.mysql.jdbc.Driver");
        GenEntity.createEntity("main.java.com.project.pojo","wlm");
    }

废话不多说，下面上代码；

package xyz.askway.util;


import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Serializable;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * xyz.askway.util（包）
 *名称:
 *功能:生成实体类
 * @author WANGLiMiN
 * 2018年7月12日/下午1:32:20
 */
public class GenEntity {
    private String packageOutPath;// 指定实体生成所在包的路径
    private String authorName;// 作者名字
    private String tablename; //  表名
    private String[] colnames; // 列名数组
    private String[] colTypes; // 列名类型数组
    private int[] colSizes; // 列名大小数组
    private Map comment; // 字段注释
    private boolean f_util = false; // 是否需要导入包java.util.*
    private boolean f_sql = false; // 是否需要导入包java.sql.*
    // 数据库连接
    private static String URL;
    private static String NAME;
    private static String PASS;
    private static String DRIVER;

    /**
     *@function:生成entity的.java文件
     *@analysis:packageOutPath：指定实体生成所在包的路径，authorName：作者名字，tablename：表名
     * @author WANGLiMiN
     * 2018年7月12日/下午7:14:45
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    private GenEntity(String packageOutPath,String authorName,String tablename) {
        this.packageOutPath=packageOutPath;
        this.authorName=authorName;
        this.tablename=tablename;
// 创建连接
        Connection con = null;
// 查要生成实体类的表
        String sql = "select * from " + tablename;
        PreparedStatement pStemt = null;
        PreparedStatement pStemt2 = null;
        try {
            try {
                Class.forName(DRIVER);
            } catch (ClassNotFoundException e1) {
                e1.printStackTrace();
            }
            con = DriverManager.getConnection(URL, NAME, PASS);
            pStemt = con.prepareStatement(sql);
            ResultSetMetaData rsmd = pStemt.getMetaData();
            int size = rsmd.getColumnCount();
// 统计列
            colnames = new String[size];
            colTypes = new String[size];
            colSizes = new int[size];
            for (int i = 0; i < size; i++) {
                colnames[i] = rsmd.getColumnName(i + 1);
                colTypes[i] = rsmd.getColumnTypeName(i + 1);
                if (colTypes[i].equalsIgnoreCase("datetime")) {
                    f_util = true;
                }
                if (colTypes[i].equalsIgnoreCase("image") || colTypes[i].equalsIgnoreCase("text")) {
                    f_sql = true;
                }
                colSizes[i] = rsmd.getColumnDisplaySize(i + 1);
            }
// 获取数据库字段注释
            String commentSql = " show full fields from " + tablename;
            comment = new HashMap();
            pStemt2 = con.prepareStatement(commentSql);
            ResultSet rs2 = pStemt2.executeQuery();
            while (rs2.next()) {
                String comm = rs2.getString("Comment");
                if (null != comm && !comm.equals("")) {
                    comment.put(rs2.getString("Field"), comm);
                } else {
                    comment.put(rs2.getString("Field"), rs2.getString("Field"));
                }
            }
//System.out.println(comment);
            String content = parse(colnames, colTypes, colSizes);
            try {
                File directory = new File("");
                String outputPath = directory.getAbsolutePath() + "\\src\\" + this.packageOutPath.replace(".", "\\")
                      + "\\";
                File file = new File(outputPath);
                file.mkdirs();
                FileWriter fw = new FileWriter(outputPath + initcap(colnameToHump(tablename)) + ".java");
                PrintWriter pw = new PrintWriter(fw);
                pw.println(content);
                pw.flush();
                pw.close();
                System.out.println("生成"+ initcap(colnameToHump(tablename)) +"实体类类成功！");
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    /**
     *@function:初始化数据库配置
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午12:32:23
     */
    public static void DatabaseInit(String URL,String userName,String userPassword,String Driver) {
        GenEntity.URL=URL;
        GenEntity.NAME=userName;
        GenEntity.PASS=userPassword;
        GenEntity.DRIVER=Driver;
    }
    /**
     *@function:创建实体类。
     *@analysis:packageOutPath： 指定实体生成所在包的路径，authorName：作者名字
     * @author WANGLiMiN
     * 2018年7月12日/下午12:19:13
     */
    public static void createEntity(String packageOutPath,String authorName) {
        try {
            try {
                Class.forName(DRIVER);
            } catch (ClassNotFoundException e1) {
                e1.printStackTrace();
            }
            for (String str : getTableNames (DriverManager.getConnection(URL, NAME, PASS))) {
                new GenEntity(packageOutPath, authorName, str);
            }
        } catch (SQLException e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }


    /**
     *@function:生成实体类主体代码
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:15:33
     */
    private String parse(String[] colnames, String[] colTypes, int[] colSizes) {
        StringBuffer sb = new StringBuffer();
        sb.append("package " + this.packageOutPath.substring(10,this.packageOutPath.length()) + ";\r\n");
        sb.append("\r\n");
// 判断是否导入工具包
        if (f_util) {
            sb.append("import java.util.Date;\r\n");
        }
        if (f_sql) {
            sb.append("import java.sql.*;\r\n");
        }
        sb.append("import java.io.Serializable;\r\n");
// 注释部分
        /**
         *2019/1/15 11:19
         *@author:wlm
         *@#function:
         *@analysis:
         */
        sb.append("\r\n");
        sb.append("/**\r\n");
        sb.append(" *@name:" + tablename + "实体类\r\n");
        sb.append(" *@function:持久化(CRUD)\r\n");
        sb.append(" *@author:"+ this.authorName + "\r\n");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        sb.append(" *"+sdf.format(new Date())+"\r\n");
        sb.append(" */");
// 实体部分
        sb.append("\r\n");
        sb.append("public class " + initcap(colnameToHump(tablename)) + " implements Serializable {\r\n");
        processAllAttrs(sb);// 属性

        processConstructor(sb);//构造方法

        processAllMethod(sb);// get/set方法

        processtoString(sb); // 重写toString()方法

        sb.append("}\r\n");
        return sb.toString();
    }

    /**
     *@function:生成toString
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午12:10:14
     */
    private void processtoString(StringBuffer sb) {
        sb.append("\r\n\t/**\r\n");
        sb.append("\t *实现:@see java.lang.Object#toString()\n");
        sb.append("\t *@function:\r\n");
        sb.append("\t *@analysis:\r\n");
        sb.append("\t *@author:"+this.authorName);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
        sb.append("\t */\n");
        sb.append("\t@Override\n");
        sb.append("\tpublic String toString() {\n\t\treturn \""+ initcap(colnameToHump(tablename)) +" [");
        for (int i = 0; i < colnames.length; i++) {
            if(i+1!=colnames.length){
                sb.append(((i+1)%3!=0)?(colnameToHump(colnames[i])+"=\" + "+colnameToHump(colnames[i])+" + \", "):("\" \n\t\t\t+\""+colnameToHump(colnames[i])+"=\" + "+colnameToHump(colnames[i])+" + \", "));
            }else {
                sb.append(colnameToHump(colnames[i])+"=\" + "+colnameToHump(colnames[i])+" + \"]\";\n\t}\n");
            }
        }
    }


    /**
     *@function:生成构造方法
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/上午11:17:46
     */
    private void processConstructor(StringBuffer sb) {
        sb.append("\r\n\t/**\r\n");
        sb.append("\t *@function:实例化对象\r\n");
        sb.append("\t *@analysis:构造方法\r\n");
        sb.append("\t *@author:"+this.authorName);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
        sb.append("\t */");
        sb.append("\n\tpublic " + initcap(colnameToHump(tablename)) + "(){};\r\n");
        sb.append("\r\n\t/**\r\n");
        sb.append("\t *@function:实例化对象并赋值\r\n");
        sb.append("\t *@analysis:构造方法\r\n");
        sb.append("\t *@author:"+this.authorName);
        sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
        sb.append("\t */");
        sb.append("\n\tpublic " + initcap(colnameToHump(tablename)) + "(");
        for (int i = 0; i < colnames.length; i++) {
            if(i+1!=colnames.length) {
                sb.append(sqlType2JavaType(colTypes[i]) + " " +colnameToHump(colnames[i])+",");
            }else {
                sb.append(sqlType2JavaType(colTypes[i]) + " " +colnameToHump(colnames[i])+"){\r\n");
                for (int j = 0; j < colnames.length; j++) {
                    sb.append("\t\tthis."+colnameToHump(colnames[j])+" = "+colnameToHump(colnames[j])+";\n");
                }
            }
        }
        sb.append("\t}\r\n");
    }
    /**
     *@function:生成entityClass的所有属性
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:15:56
     */
    private void processAllAttrs(StringBuffer sb) {
        sb.append("\r\n\t/**\r\n");
        sb.append("\t *@function:\r\n");
        sb.append("\t *@analysis:\r\n");
        sb.append("\t *@author:"+this.authorName);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
        sb.append("\t */\r\n");
        sb.append("\tprivate static final long serialVersionUID = 1L;\r\n\n");


        for (int i = 0; i < colnames.length; i++) {
            sb.append("\tprivate " + sqlType2JavaType(colTypes[i]) + " " + colnameToHump(colnames[i]) + ";  //"+comment.get(colnames[i]) +"\r\n");
        }
    }



    /**
     *@function:生成getter,setter方法
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:16:30
     */
    private void processAllMethod(StringBuffer sb) {
        for (int i = 0; i < colnames.length; i++) {
            sb.append("\r\n\t/**\r\n");
            sb.append("\t *@function:获得"+comment.get(colnames[i])+"\r\n");
            sb.append("\t *@analysis:\r\n");
            sb.append("\t *@author:"+this.authorName);
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
            sb.append("\t */\r\n");
            sb.append("\tpublic " + sqlType2JavaType(colTypes[i]) + " get" + initcap(colnameToHump(colnames[i]))
                  + "(){\r\n");
            sb.append("\t\treturn " + colnameToHump(colnames[i]) + ";\r\n");
            sb.append("\t}\r\n");
            sb.append("\r\n");
            sb.append("\t/**\r\n");
            sb.append("\t *@function:设置"+colnames[i]+"\r\n");
            sb.append("\t *@analysis:\r\n");
            sb.append("\t *@author:"+this.authorName);
            sb.append("\r\n\t *"+sdf.format(new Date())+"\r\n");
            sb.append("\t */\r\n");
            sb.append("\tpublic void set" + initcap(colnameToHump(colnames[i])) + "(" + sqlType2JavaType(colTypes[i])
                  + " " + colnameToHump(colnames[i]) + "){\r\n");
            sb.append("\t\tthis." + colnameToHump(colnames[i]) + " = " + colnameToHump(colnames[i]) + ";\r\n");
            sb.append("\t}\r\n");
            sb.append("\r\n");
        }

    }


/** 
 *@function:将数据库的字段改成驼峰命名的方式 (将每个单词的首字母大写)
 *@analysis:
 * @author WANGLiMiN
 * 2018年7月12日/下午7:16:42
 */
 public String colnameToHump(String colnames) {
        String[] tf = colnames.split("_");
        String newColName = "";
        for(int i=0;i<tf.length;i++) {
            if(!tf[i].equalsIgnoreCase("TB")) {
                tf[i] = initcap(tf[i]);
     newColName += tf[i];
            }else
                newColName+="Entity";
        }
        return newColName;


    }


    /**
     *@function:将输入字符串的首字母改成大写
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:17:17
     */
    private String initcap(String str) {
        char[] ch = str.toCharArray();
        if (ch[0] >= 'a' && ch[0] <= 'z') {
            ch[0] = (char) (ch[0] - 32);
        }
        return new String(ch);
    }


    /**
     *@function:获得列的数据类型 
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:17:27
     */
    private String sqlType2JavaType(String sqlType) {
        if (sqlType.equalsIgnoreCase("bit")) {
            return "Boolean";
        } else if (sqlType.equalsIgnoreCase("tinyint")) {
            return "byte";
        } else if (sqlType.equalsIgnoreCase("smallint")) {
            return "short";
        } else if (sqlType.equalsIgnoreCase("int")) {
            return "Integer";
        } else if (sqlType.equalsIgnoreCase("bigint")) {
            return "Long";
        } else if (sqlType.equalsIgnoreCase("float")) {
            return "Float";
        } else if (sqlType.equalsIgnoreCase("decimal") || sqlType.equalsIgnoreCase("numeric")
              || sqlType.equalsIgnoreCase("real") || sqlType.equalsIgnoreCase("money")
              || sqlType.equalsIgnoreCase("smallmoney")) {
            return "Double";
        } else if (sqlType.equalsIgnoreCase("varchar") || sqlType.equalsIgnoreCase("char")
              || sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nchar")
              || sqlType.equalsIgnoreCase("text")) {
            return "String";
        } else if (sqlType.equalsIgnoreCase("datetime")) {
            return "Date";
        } else if (sqlType.equalsIgnoreCase("image")) {
            return "Blod";
        }
        return "String";
    }


    /**
     *@function:获取数据库下的所有表名
     *@analysis:
     * @author WANGLiMiN
     * 2018年7月12日/下午7:17:36
     */
    public static List<String> getTableNames(Connection conn) {
        List<String> tableNames = new ArrayList<>();
        ResultSet rs = null;
        try {
// 获取数据库的元数据
            DatabaseMetaData db = conn.getMetaData();
// 从元数据中获取到所有的表名
            rs = db.getTables(null, null, null, new String[] { "TABLE" });
            while (rs.next()) {
                tableNames.add(rs.getString(3));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return tableNames;
    }




}