自动生成java实体类的工具类

写实体类的悲伤

写一个java实体类，需要对着数据库的表来写，还要写注释，注解，虽然可以一键生成get和set方法，
但是当表字段非常多的时候，真的是挺烦的一件事情，
我一直信奉一个观念，能自动化的，就不要动手了，写代码也应该是一样，
很多人都知道，mybatis提供的生成器，可以生成实体类啊，dao啊，还有xml，多方便，
但是我开发的数据库的表的字段特殊啊，于是自己网上找个例子，然后照着写了一个，强行装逼，
从此，实体类，dao，xml一键生成，完美！

自动生成的本质

所谓自动生成对应的类，其本质也是使用代码，拼凑java类的代码字符串内容，然后生成一个file，
把内容流写入，在项目对应路径下直接生成一个需要的文件，当然，只适用于格式固定，有规律的类。

代码示例

（1）初始化全局常量，以及定义对应变量

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/**
 * 数据库配置
 */
private final static String pgUrl = "jdbc:postgresql://192.168.1.69:5432/test_db";
private final static String username = "dbuser";
private final static String password = "123456";
/**
 * 包路径配置
 */
private final static String domain = "com.test.domain";
private final static String mapper = "com.test.mapper";
private final static String I_mapper = "com.test.mapper";
private final static String mapper_impl = "com.test.mapper.impl";
private final static String I_service = "com.test.service";
private final static String service_impl = "com.test.service.impl";
//表名
private String tableNames = "";
// 全列名数组（没有做大小写转换,没有去除字段前缀）
private String[] all_colnames;
// 列名类型数组
private String[] col_types; 
// 列注释数组
private String[] col_remarks; 
// 是否需要导入包java.util.Date
private boolean is_util = false; 
//作者
private String authors = "lmshe";

（2）获取数据库连接，并初始化相关变量

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public void generatorUtils(String tableName,String author){
	
	tableNames = tableName;
	authors = author;
	
	Connection conn = null; 
	PreparedStatement pstmt = null;
	try {
		// 得到数据库连接
		conn = DriverManager.getConnection(pgUrl, username, password);
		String strsql = "select * from " + tableName;
		pstmt = conn.prepareStatement(strsql);
		ResultSetMetaData rsmd = pstmt.getMetaData();
		
		// 查询该表共有多少列，并初始化相关数组
		int size = rsmd.getColumnCount(); 
		all_colnames = new String[size];
		col_types = new String[size];
		col_remarks = new String[size];
		
		//初始化列注释
		DatabaseMetaData dbmd = conn.getMetaData();
		ResultSet rs = dbmd.getColumns(null, null, tableName, null);
		int re = 0;
		while (rs.next()) {
			String remarks = rs.getString("REMARKS");// 列描述
			col_remarks[re] = remarks;
			re++;
		}
		
		//初始化列名以及列的字段类型，同时初始化是否需要导入java.util.Date
		for (int i = 0; i < rsmd.getColumnCount(); i++) {
			all_colnames[i] = rsmd.getColumnName(i + 1);
			col_types[i] = rsmd.getColumnTypeName(i + 1);
			if (rsmd.getColumnTypeName(i + 1).equalsIgnoreCase("timestamp")) {
				is_util = true;
			}
		}
		
		//生成domain实体类
		createDomainUtils();
		//生成sql的xml
		createMappingUtils();
		//生成dao接口类
		createIDaoUtils();
		//生成dao实现类
		createDaoImplUtils();
	} catch (SQLException e) {
		e.printStackTrace();
	} finally {
		try {
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}

（3）生成domain类

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public void createDomainUtils() {
	try {
		String content = parseDomain();
		String path = System.getProperty("user.dir") + "/src/main/java/" + domain.replaceAll("\\.", "/");
		File file = new File(path);
		if (!file.exists()) {
			file.mkdirs();
		}
		String resPath = path + "/" + initcap(tableNames.substring(2, tableNames.length())) + ".java";
		FileUtils.writeStringToFile(new File(resPath), content);
		System.out.println("建立domain成功");
	} catch (Exception e) {
		e.printStackTrace();
	}
}
private String parseDomain() {
	StringBuffer sb = new StringBuffer();
	sb.append("package " + domain + ";\r\n\r\n");
	//导入依赖包
	if (is_util) {
		sb.append("import java.util.Date;\r\n\r\n");
	}
	sb.append("import javax.persistence.Column;\r\n");
	sb.append("import javax.persistence.Id;\r\n");
	sb.append("import javax.persistence.Table;\r\n\r\n");
	//添加注解
	sb.append("/**\r\n");
	sb.append(" *\r\n");
	sb.append(" * @author " + authors + "\r\n");
	SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
	String date = sf.format(new Date());
	sb.append(" * @time " + date + "\r\n");
	sb.append(" * @desc \r\n");
	sb.append(" */\r\n");
	//类主体
	sb.append("@Table(name=\"" + tableNames + "\")\r\n");
	sb.append("public class " + initcap(tableNames.substring(2))
			+ " {\r\n\r\n");
	//生成属性
	processAllAttrs(sb);
	sb.append("\r\n");
	//生成方法
	processAllMethod(sb);
	sb.append("}\r\n");
	return sb.toString();
}
private void processAllMethod(StringBuffer sb) {
	for (int i = 0; i < all_colnames.length; i++) {
		String allColname = all_colnames[i];
		String colname = getCamelStr(allColname);
		if (colname.substring(0, 1).equals("f")) {
			colname = colname.substring(1);
		}
		sb.append("\tpublic void set" + initcap(colname) + "(" + sqlType2JavaType(col_types[i]) + " " + colname
				+ "){\r\n");
		sb.append("\t\tthis." + colname + "=" + colname + ";\r\n");
		sb.append("\t}\r\n\r\n");
		sb.append("\tpublic " + sqlType2JavaType(col_types[i]) + " get" + initcap(colname) + "(){\r\n");
		sb.append("\t\treturn " + colname + ";\r\n");
		sb.append("\t}\r\n\r\n");
	}
}
private void processAllAttrs(StringBuffer sb) {
	for (int i = 0; i < all_colnames.length; i++) {
		String remark = col_remarks[i];
		if (remark != null) {
			sb.append("\t/**\r\n");
			sb.append("\t * " + remark + "\r\n");
			sb.append("\t */\r\n");
		}
		String allColname = all_colnames[i];
		String colname = getCamelStr(allColname);
		if (allColname.equals("id")) {
			sb.append("\t@Id\r\n");
			sb.append("\t@Column(name = \""+allColname+"\")\r\n");
		} else {
			sb.append("\t@Column(name=\"" + allColname + "\")\r\n");
		}
		if (colname.substring(0, 1).equals("f")) {
			colname = colname.substring(1);
		}
		sb.append("\tprivate " + sqlType2JavaType(col_types[i]) + " " + colname + ";\r\n\r\n");
	}
}

（4）生成sql的xml

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public void createMappingUtils() {
	try {
		String content = parseMapping();
		String path = System.getProperty("user.dir") + "/src/main/java/" + mapper.replaceAll("\\.", "/");
		File file = new File(path);
		if (!file.exists()) {
			file.mkdirs();
		}
		String resPath = path + "/I" + initcap(tableNames.substring(2, tableNames.length())) + "Mapper.xml";
		FileUtils.writeStringToFile(new File(resPath), content);
		System.out.println("建立xml成功");
	} catch (Exception e) {
		e.printStackTrace();
	}
}
private String parseMapping() {
	StringBuffer sb = new StringBuffer();
	sb.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n");
	sb.append("<!DOCTYPE mapper PUBLIC \"-//mybatis.org//DTD Mapper 3.0//EN\" \"http://mybatis.org/dtd/mybatis-3-mapper.dtd\">\r\n\r\n");
	sb.append("<mapper namespace=\"com.unionbon.youlb.http.mapper.I"+initcap(tableNames.substring(2))+"Mapper\">\r\n\r\n");
	sb.append("\t<resultMap id=\"BaseResultMap\" type=\"com.unionbon.youlb.http.domain."+initcap(tableNames.substring(2))+"\">\r\n");
	
	for (int i = 0; i < all_colnames.length; i++) {
		String allColname = all_colnames[i];
		String colname = getCamelStr(allColname);
		if (allColname.equals("id")) {
			sb.append("\t\t<id column=\"id\" property=\"id\" jdbcType=\""+sqlType2MybatisType(col_types[i])+"\" />\r\n");
		} else {
			if (colname.substring(0, 1).equals("f")) {
				colname = colname.substring(1);
			}
			sb.append("\t\t<result column=\""+allColname+"\" property=\""+colname+"\" jdbcType=\""+sqlType2MybatisType(col_types[i])+"\" />\r\n");
		}
	}
	sb.append("\t</resultMap>\r\n");
	sb.append("</mapper>");
	return sb.toString();
}

（5）生成dao以及实现类

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public void createIDaoUtils() {
	try {
		String content = parseIDao();
		String path = System.getProperty("user.dir") + "/src/main/java/" + I_mapper.replaceAll("\\.", "/");
		File file = new File(path);
		if (!file.exists()) {
			file.mkdirs();
		}
		String resPath = path + "/I" + initcap(tableNames.substring(2, tableNames.length())) + "Mapper.java";
		FileUtils.writeStringToFile(new File(resPath), content);
		System.out.println("建立dao接口类成功");
	} catch (Exception e) {
		e.printStackTrace();
	}
}
private String parseIDao() {
	StringBuffer sb = new StringBuffer();
	sb.append("package " + I_mapper + ";\r\n\r\n");
	sb.append("import com.unionbon.youlb.http.mapper.IBaseMapper;\r\n");
	sb.append("import com.unionbon.youlb.http.domain."+initcap(tableNames.substring(2))+";\r\n\r\n");
	//添加注解
	sb.append("/**\r\n");
	sb.append(" *\r\n");
	sb.append(" * @author " + authors + "\r\n");
	SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
	String date = sf.format(new Date());
	sb.append(" * @time " + date + "\r\n");
	sb.append(" * @desc \r\n");
	sb.append(" */\r\n");
	//类主体
	String idType = "";
	for (int i = 0; i < all_colnames.length; i++) {
		String allColname = all_colnames[i];
		if (allColname.equals("id")) {
			idType = sqlType2JavaType(col_types[i]);
			break;
		}
	}
	sb.append("public interface I" + initcap(tableNames.substring(2)) + "Mapper extends IBaseMapper<"+initcap(tableNames.substring(2))+", "+idType+">{\r\n\r\n");
	sb.append("}\r\n");
	return sb.toString();
}
public void createDaoImplUtils() {
	try {
		String content = parseDaoImpl();
		String path = System.getProperty("user.dir") + "/src/main/java/" + mapper_impl.replaceAll("\\.", "/");
		File file = new File(path);
		if (!file.exists()) {
			file.mkdirs();
		}
		String resPath = path + "/" + initcap(tableNames.substring(2, tableNames.length())) + "MapperImpl.java";
		FileUtils.writeStringToFile(new File(resPath), content);
		System.out.println("建立dao实现类成功");
	} catch (Exception e) {
		e.printStackTrace();
	}
}
private String parseDaoImpl() {
	StringBuffer sb = new StringBuffer();
	sb.append("package " + mapper_impl + ";\r\n\r\n");
	sb.append("import com.unionbon.youlb.http.mapper.impl.BaseMapperImpl;\r\n");
	sb.append("import com.unionbon.youlb.http.mapper.I"+initcap(tableNames.substring(2))+"Mapper;\r\n");
	sb.append("import com.unionbon.youlb.http.domain."+initcap(tableNames.substring(2))+";\r\n\r\n");
	//添加注解
	sb.append("/**\r\n");
	sb.append(" *\r\n");
	sb.append(" * @author " + authors + "\r\n");
	SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
	String date = sf.format(new Date());
	sb.append(" * @time " + date + "\r\n");
	sb.append(" * @desc \r\n");
	sb.append(" */\r\n");
	//类主体
	String idType = "";
	for (int i = 0; i < all_colnames.length; i++) {
		String allColname = all_colnames[i];
		if (allColname.equals("id")) {
			idType = sqlType2JavaType(col_types[i]);
			break;
		}
	}
	sb.append("public class " + initcap(tableNames.substring(2)) + "MapperImpl extends BaseMapperImpl<"+initcap(tableNames.substring(2))+", "+idType+"> implements I"+initcap(tableNames.substring(2))+"Mapper{\r\n\r\n");
	sb.append("}\r\n");
	return sb.toString();
}

（6）工具方法

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/**
 * 把输入字符串的首字母改成大写
 * 
 * @param str
 * @return
 */
public static String initcap(String str) {
	char[] ch = str.toCharArray();
	if (ch[0] >= 'a' && ch[0] <= 'z') {
		ch[0] = (char) (ch[0] - 32);
	}
	return getCamelStr(new String(ch));
}
/**
 * 
 * @param s
 * @return
 * @author lmshe
 * @time 2017年3月30日
 * @desc 处理下横杠，并转为大写
 */
public static String getCamelStr(String s) {
	while (s.indexOf("_") > 0) {
		int index = s.indexOf("_");
		s = s.substring(0, index) + s.substring(index + 1, index + 2).toUpperCase() + s.substring(index + 2);
	}
	return s;
}
/**
 * 
 * @param sqlType
 * @return
 * @author lmshe
 * @time 2017年3月30日
 * @desc 数据库类型与java类型互转
 */
private String sqlType2JavaType(String sqlType) {
	if (sqlType.equalsIgnoreCase("bit")) {
		return "bool";
	} else if (sqlType.equalsIgnoreCase("tinyint")) {
		return "byte";
	} else if (sqlType.equalsIgnoreCase("int2")) {
		return "short";
	} else if (sqlType.equalsIgnoreCase("int4") || sqlType.equals("serial")) {
		return "Integer";
	} else if (sqlType.equalsIgnoreCase("int8")) {
		return "Long";
	} 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")) {
		return "double";
	} else if (sqlType.equalsIgnoreCase("money") || sqlType.equalsIgnoreCase("smallmoney")) {
		return "double";
	} else if (sqlType.equalsIgnoreCase("varchar") || sqlType.equalsIgnoreCase("char")
			|| sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nchar")) {
		return "String";
	} else if (sqlType.equalsIgnoreCase("timestamp")) {
		return "Date";
	} else if (sqlType.equalsIgnoreCase("image")) {
		return "Blob";
	} else if (sqlType.equalsIgnoreCase("text")) {
		return "Clob";
	}
	return null;
}
/**
 * 
 * @param sqlType
 * @return
 * @author lmshe
 * @time 2017年3月31日
 * @desc 数据库类型与mybatisxml的jdbc类型转换
 */
private String sqlType2MybatisType(String sqlType) {
	if (sqlType.equalsIgnoreCase("int4") || sqlType.equals("serial")) {
		return "INTEGER";
	} else if (sqlType.equalsIgnoreCase("varchar")) {
		return "VARCHAR";
	} else if (sqlType.equalsIgnoreCase("char")){
		return "CHAR";
	}else if (sqlType.equalsIgnoreCase("timestamp")) {
		return "TIMESTAMP";
	}else if(sqlType.equalsIgnoreCase("decimal")){
		return "DECIMAL";
	}
	return null;
}

（7）测试

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/**
 * 
 * 
 * @author lmshe
 * @time 2017年3月30日
 * @desc 代码生成器
 */
public class Generator {
	//表名
	private final static String tableName= "t_users";
	//作者
	private  final static String author = "lmshe";
	//生成代码仅适用于表主键字段名为“id”，且其它字段以“f”开始,且字段都以下横杠连接
	public static void main(String[] args) {
		new GeneratorUtils().generatorUtils(tableName,author);
	}
}

寄语

当人生活成了回忆，不过是在等待逝去，而只有不断创造回忆，才是人生精彩的演绎