Db4o一个轻巧的、面向对象的数据库。为了方便调用，这里将查询、插入、更新、删除操作封装到了Db4oUtil工具类，懒人可一键调用

 import com.db4o.Db4o; import com.db4o.ObjectContainer; import com.db4o.query.Query; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; import java.lang.reflect.Field; import java.util.*; / * @Author: yuc * @Description: * @Date: */ / // db4o 版本 <dependency> <groupId>com.db4o</groupId> <artifactId>db4o-core-java5</artifactId> <version>8.0.184.15484</version> </dependency> */ @Component public class Db4oUtil { 
    private static Logger logger = LoggerFactory.getLogger(Db4oUtil.class); // 通过此方式向静态变量赋值 @Value("${db4o.database.name}") private void setDatabaseName(String databaseName) { 
    Db4oUtil.databaseName = databaseName; } // 数据库文件名（全路径: ./.db/test_DB.yap） private static String databaseName; / * 条件查询 * * @param clazz 返回对象 * @param descend 列名 * @param constrain 查询的值 * @param <T> * @return */ public synchronized static <T> List<T> searchLimit(Class clazz, String descend, String constrain) { 
    ObjectContainer db = null; try { 
    db = Db4o.openFile(databaseName); Query query = db.query(); query.constrain(clazz); query.descend(descend).constrain(constrain); List<T> results = query.execute(); if (results == null || results.size() <= 0) { 
    return null; } else { 
    return new ArrayList<>(results); } } catch (Exception e) { 
    logger.error("查询操作失败", e); return null; } finally { 
    if (db != null) db.close(); } } / * 查询所有 * * @param clazz 返回对象 * @param <T> * @return */ public synchronized static <T> List<T> search(Class clazz) { 
    ObjectContainer db = null; try { 
    db = Db4o.openFile(databaseName); Query query = db.query(); query.constrain(clazz); List<T> results = query.execute(); if (results == null || results.size() <= 0) { 
    return null; } else { 
    return new ArrayList<>(results); } } catch (Exception e) { 
    logger.error("查询操作失败", e); return null; } finally { 
    if (db != null) db.close(); } } / * 插入数据 * * @param T * @return */ public synchronized static <T> boolean create(T T) { 
    ObjectContainer db = null; try { 
    db = Db4o.openFile(databaseName); db.store(T); db.commit(); return true; } catch (Exception e) { 
    logger.error("创建操作失败", e); return false; } finally { 
    if (db != null) db.close(); } } / * 更新数据，需要先查询到数据，再对数据进行修改 * * @param clazz 返回对象 * @param descend 查询的列名 * @param constrain 查询的值 * @param map 要更新的数据，格式为 (要更新的列名, 要更新的值) * @param <T> * @return */ public synchronized static <T> boolean updateLimit(Class clazz, String descend, String constrain, Map<Object, Object> map) { 
    ObjectContainer db = null; try { 
    db = Db4o.openFile(databaseName); Query query = db.query(); query.constrain(clazz); query.descend(descend).constrain(constrain); List<T> results = query.execute(); if (results == null || results.size() <= 0) { 
    return false; } else { 
    Object object = results.get(0); Set<Map.Entry<Object, Object>> entries = map.entrySet(); for (Map.Entry entry : entries) { 
    Field declaredField = clazz.getDeclaredField(entry.getKey().toString()); declaredField.setAccessible(true); declaredField.set(object, entry.getValue()); } db.store(object); db.commit(); return true; } } catch (Exception e) { 
    logger.error("更新操作失败", e); return false; } finally { 
    if (db != null) db.close(); } } / * 删除对象并校验，和更新操作一样，需要先查询 * * @param clazz 返回对象 * @param descend 查询的列名 * @param constrain 查询的值 * @param confirmFiledName 要删除的列名 * @param confirmData 要删除列名对应的值 * @param <T> * @return */ public synchronized static <T> boolean delete(Class clazz, String descend, String constrain, String confirmFiledName, String confirmData) { 
    ObjectContainer db = null; try { 
    db = Db4o.openFile(databaseName); Query query = db.query(); query.constrain(clazz); query.descend(descend).constrain(constrain); List<T> results = query.execute(); if (results == null || results.size() <= 0) { 
    return false; } else { 
    Object object = results.get(0); Field declaredField = clazz.getDeclaredField(confirmFiledName); declaredField.setAccessible(true); if (declaredField.get(object).equals(confirmData)) { 
    db.delete(object); db.commit(); return true; } else return false; } } catch (Exception e) { 
    logger.error("删除操作失败", e); return false; } finally { 
    if (db != null) db.close(); } } }