使用Groovy 动态编译生成class文件，再结合 easyexcel 导出excel
前提
easyexcel 的使用必须要有实体类，然后根据实体类上的注解@ExcelProperty 实现，根据字段导出数据到excel中
缺点
必须要具有一个entity.java 文件，如果只是为了解决日常的解决问题，那么当遇到需要导出excel的问题时，就要再生成一个对应的java文件，这样就很麻烦了，如果在工作中，那么就需要大量繁琐的实体java文件
解决办法
只需要输入表名、列名，查询数据库结果，动态编译生成class文件，然后使用生成的class文件作为实体和数据库结果进行excel数据的导出。
- 依赖文件，需要 mysql、easyexcel、groovy
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.19</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.2.10</version>
</dependency>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-all</artifactId>
<version>2.4.13</version>
</dependency>
- 具体工具类
package com.rule.utils;
import com.alibaba.excel.EasyExcelFactory;
import groovy.lang.GroovyClassLoader;
import org.springframework.util.Assert;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class GenEntityUtil {
private static String tableName;
private static String queryFields;
/**
* 解析处理(生成实体类主体代码)
*/
private static String parse(String[] colNames) {
StringBuilder sb = new StringBuilder();
sb.append("package com.rule.pojo;").append("\n");
sb.append("import com.alibaba.excel.annotation.ExcelProperty;").append("\n\n");
sb.append("public class ").append(camelStr(tableName, true)).append(" {\r\n");
processAllAttrs(sb, colNames);
processAllMethod(sb, colNames);
sb.append("}\r\n");
System.out.println(sb.toString());
return sb.toString();
}
/**
* 生成所有的方法
*
* @param sb
*/
private static void processAllMethod(StringBuilder sb, String[] colNames) {
for (String colname : colNames) {
sb.append("\tpublic " + "String" + " get").append(camelStr(colname, true)).append("(){\r\n");
sb.append("\t\treturn ").append(camelStr(colname)).append(";\r\n");
sb.append("\t}\r\n");
sb.append("\tpublic void set").append(camelStr(colname, true)).append("(").append("String").append(" ").append(camelStr(colname)).append("){\r\n");
sb.append("\t\tthis.").append(camelStr(colname)).append(" = ").append(camelStr(colname)).append(";\r\n");
sb.append("\t}\r\n");
}
}
/**
* 解析输出属性
*
* @return
*/
private static void processAllAttrs(StringBuilder sb, String[] colNames) {
for (String colname : colNames) {
sb.append("\t@ExcelProperty(\"").append(colname).append("\")\r\n");
sb.append("\tprivate " + "String" + " ").append(camelStr(colname)).append(";\r\n");
}
}
/**
* 把输入字符串的首字母改成大写, 下划线的colName转换为驼峰
*
* @param str colName
* @return camel name
*/
private static String camelStr(String str, boolean... method) {
char[] ch = str.toCharArray();
for (int i = 1; i < ch.length; i++) {
if (ch[i - 1] == '_') {
ch[i] = (char) (ch[i] - 32);
}
}
if (method.length > 0) {
ch[0] = (char) (ch[0] - 32);
}
return new String(ch).replace("_", "");
}
/**
* 获取项目所在路径
*
* @return
*/
public static String getRealPath() throws IOException {
String realPath = GenEntityUtil.class.getClassLoader().getResource("").getPath();
realPath = realPath + File.separator + "com" +
File.separator + "rule" +
File.separator + "pojo" +
File.separator;
try {
//路径decode转码
realPath = java.net.URLDecoder.decode(realPath, "utf-8");
} catch (Exception e) {
e.printStackTrace();
}
return realPath;
}
public static void doGen() throws Exception {
String[] columnNames = queryFields.split(",");
String content = parse(columnNames);
GroovyClassLoader groovyClassLoader = new GroovyClassLoader();
Class<?> clazz = groovyClassLoader.parseClass(content);
export(clazz, data(clazz, columnNames, getData()));
}
public static List<Object> data(Class<?> loadClass, String[] columnNames, List<String[]> rawData) throws Exception {
List<Object> data = new ArrayList<>(rawData.size());
for (String[] rawDatum : rawData) {
Object instance = loadClass.newInstance();
for (int i = 0; i < rawDatum.length; i++) {
String field = camelStr(columnNames[i], true);
Method method = loadClass.getDeclaredMethod("set" + field, String.class);
method.invoke(instance, rawDatum[i]);
}
data.add(instance);
}
return data;
}
public static void export(Class<?> clazz, List<Object> tableList) {
String fileName = "C:\\Users\\rulelau\\Desktop\\" + System.currentTimeMillis() + ".xlsx";
EasyExcelFactory.write(fileName, clazz).sheet("sheet1").doWrite(tableList);
}
public static void main(String[] args) throws Exception {
tableName = "undo_log";
queryFields = "branch_id,xid,context,rollback_info,log_status,log_created,log_modified";
doGen();
}
public static List<String[]> getData() {
List<String[]> checkTables = new ArrayList<>(10000);
String[] allArray = queryFields.split(",");
String sql = "SELECT " + queryFields + " FROM " + tableName;
Connection con = Conn.getConnection();
Assert.notNull(con, "con 连接对象不能为空");
try (PreparedStatement statement = con.prepareStatement(sql)) {
ResultSet rs = statement.executeQuery();
while (rs != null && rs.next()) {
String[] fieldValues = new String[allArray.length];
for (int i = 0; i < allArray.length; i++) {
Object value = rs.getObject(allArray[i]);
fieldValues[i] = value == null ? null : value.toString();
}
checkTables.add(fieldValues);
}
} catch (SQLException e) {
e.printStackTrace();
}
return checkTables;
}
public static class Conn {
private static Connection conn;
public static Connection getConnection() {
if (conn != null) {
return conn;
}
String url = "jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&serverTimezone=Asia/Shanghai";
String Driver = "com.mysql.cj.jdbc.Driver";
String Userid = "root";
String Password = "123456";
try {
Class.forName(Driver);
System.out.println(url);
conn = DriverManager.getConnection(url, Userid, Password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
}
}
```
效果
-
生成的class文件
-
下载的文件
