SpringDataJPA中出现的保存出现的Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist:

出现这种问题是先看看自己的实体类主键策略

通常原因分两种：

[email protected](strategy=GenerationType.IDENTITY)

    这种主键策略是自增长，数据库中设置主键自增和在对应的实体类中设置对应的主键自增，只要有哪一边没有设置，就会报该异常

2.我的数据表主键不是自增长，如图

这是我自己写的主键生成策略

*主键生成工具类

import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;

public class PrimaryKeyAlgorithmUtil {

    private static final long ONE_STEP = 10;    private static final Lock LOCK = new ReentrantLock();    private static long lastTime = System.currentTimeMillis();    private static short lastCount = 0;    private static int count = 0;

    @SuppressWarnings("finally")    public static Long nextId()    {        LOCK.lock();        try {            if (lastCount == ONE_STEP) {                boolean done = false;                while (!done) {                    long now = System.currentTimeMillis();                    if (now == lastTime) {                        try {                            Thread.currentThread();                            Thread.sleep(1);                        } catch (java.lang.InterruptedException e) {                        }                        continue;                    } else {                        lastTime = now;                        lastCount = 0;                        done = true;                    }                }            }            count = lastCount++;        }        finally        {            LOCK.unlock();            return Long.parseLong(lastTime+""+String.format("%03d",count));        }    }}

*主键生成器

import org.hibernate.MappingException;import org.hibernate.engine.spi.SharedSessionContractImplementor;import java.io.Serializable;

public class PrimaryKeyGenerator  extends IdentityGenerator {

    @Override    public Serializable generate(SharedSessionContractImplementor session, Object object) throws MappingException {        Object id = PrimaryKeyAlgorithmUtil.nextId();        if (id != null) {            return (Serializable) id;        }        return super.generate(session, object);    }*实体类



上图权限类和用户类为多对多的对应关系 现要插入一个，用户有多个权限当项目启动后调这个方法会出现异常这是因为数据表主键没有设置自增长，实体类也没设置id数据无法保存只需要给实体setId(id)即可解决。

原文地址：https://www.cnblogs.com/zhanggguoqi/p/11718864.html