spring的事務傳播屬性required_nested的原理介紹
本文講解"spring的事務傳播屬性required_nested的原理介紹"，希望能夠解決相關問題。
傳統(tǒng)事務中回滾點的使用
package?com.morris.spring.demo.jdbc;
import?java.sql.*;
/**
?*?傳統(tǒng)jdbc中回滾點的使用
?*/
public?class?traditionsavepointdemo?{
public?static?void?main(string[]?args)?throws?sqlexception?{
string?url?=?"jdbc:mysql://127.0.0.1:3306/test?useunicode=true&allowmultiqueries=true&characterencoding=utf-8&usefastdateparsing=false&zerodatetimebehavior=converttonull";
string?username?=?"user";
string?password?=?"user";
connection?connection?=?drivermanager.getconnection(url,?username,?password);
connection.setautocommit(false);?//?不自動提交
savepoint?one?=?connection.setsavepoint("one");
savepoint?two?=?null;
try?{
statement?statement?=?connection.createstatement();
statement.execute("insert?into?t_good(good_name,?price)?values('iphone14',?9999)");
statement.close();
two?=?connection.setsavepoint("two");
}?catch?(exception?e)?{
e.printstacktrace();
connection.rollback(one);?//?回滾事務
}
try?{
statement?statement?=?connection.createstatement();
statement.execute("insert?into?t_good(good_name,?price)?values('iphone15',?9999)");
statement.close();
boolean?flag?=?true;
if(flag)?{
throw?new?runtimeexception("xxxx");
}
}?catch?(exception?e)?{
e.printstacktrace();
connection.rollback(two);?//?回滾事務
}
connection.commit();
}
}在一個事務中可以指定回滾事務到某一個階段，實現(xiàn)精確控制事務。
事務的傳播屬性nested
在spring中，要想使用事務中的回滾點，可以使用傳播屬性nested。
com.morris.spring.service.transactionservice#addgoodandarea
@transactional(propagation?=?propagation.required)
public?void?addgoodandarea()?{
system.out.println("------addgoodandarea-------");
goodservice.addgood();
areaservice.addarea(0);
}com.morris.spring.service.areaserviceimpl#addarea
@transactional(propagation?=?propagation.nested)
@override
public?boolean?addarea(int?i)?{
int?y?=?1000000?/?i;
area?area?=?new?area();
area.setareacode(y);
area.setareaname("shenzhen");
return?areadao.insert(area);
}com.morris.spring.service.goodserviceimpl#addgood
@transactional(propagation?=?propagation.nested)
@override
public?boolean?addgood()?{
good?good?=?new?good();
good.setgoodname("iphone");
good.setprice(bigdecimal.valueof(99999));
return?gooddao.insert(good);
}運行結果如下：
debug?datasourcetransactionmanager:384?-?creating?new?transaction?with?name?[com.morris.spring.service.transactionservice.addgoodandarea]:?propagation_required,isolation_default debug?drivermanagerdatasource:144?-?creating?new?jdbc?drivermanager?connection?to?[jdbc:mysql://127.0.0.1:3306/test?useunicode=true&allowmultiqueries=true&characterencoding=utf-8&usefastdateparsing=false&zerodatetimebehavior=converttonull] debug?datasourcetransactionmanager:267?-?acquired?connection?[com.mysql.cj.jdbc.connectionimpl@8ef162]?for?jdbc?transaction debug?datasourcetransactionmanager:285?-?switching?jdbc?connection?[com.mysql.cj.jdbc.connectionimpl@8ef162]?to?manual?commit ------addgoodandarea------- debug?datasourcetransactionmanager:477?-?creating?nested?transaction?with?name?[com.morris.spring.service.goodserviceimpl.addgood] debug?jdbctemplate:860?-?executing?prepared?sql?update debug?jdbctemplate:609?-?executing?prepared?sql?statement?[insert?into?t_good(good_name,?price)?values(?,?)] debug?datasourcetransactionmanager:767?-?releasing?transaction?savepoint debug?datasourcetransactionmanager:477?-?creating?nested?transaction?with?name?[com.morris.spring.service.areaserviceimpl.addarea] debug?datasourcetransactionmanager:870?-?rolling?back?transaction?to?savepoint debug?datasourcetransactionmanager:877?-?initiating?transaction?rollback debug?datasourcetransactionmanager:347?-?rolling?back?jdbc?transaction?on?connection?[com.mysql.cj.jdbc.connectionimpl@8ef162] debug?datasourcetransactionmanager:392?-?releasing?jdbc?connection?[com.mysql.cj.jdbc.connectionimpl@8ef162]?after?transaction java.lang.arithmeticexception:?/?by?zero ...?...
發(fā)現(xiàn)整個事務都已經回滾了，按照回滾點的邏輯，addarea()方法拋出異常，不是應該只回滾到addarea()前嗎，也就是addgood()應該被提交，這是為什么呢？
如果我們將addarea()方法try catch起來，就能得到我們想要的結果，addgood()被提交，而addarea()回滾，這又是為什么呢？我們帶著這幾個問題來分析源碼。
addareaandgood()開啟事務
addareaandgood()開啟事務，最外層方法使用傳播屬性propagation_required、propagation_requires_new、propagation_nested效果都一樣，都是開啟一個新的事務。
org.springframework.transaction.support.abstractplatformtransactionmanager#gettransaction
else?if?(def.getpropagationbehavior()?==?transactiondefinition.propagation_required?||
def.getpropagationbehavior()?==?transactiondefinition.propagation_requires_new?||
def.getpropagationbehavior()?==?transactiondefinition.propagation_nested)?{
//?第一次進來
suspendedresourcesholder?suspendedresources?=?suspend(null);
if?(debugenabled)?{
logger.debug("creating?new?transaction?with?name?["?+?def.getname()?+?"]:?"?+?def);
}
try?{
//?開啟新事務
return?starttransaction(def,?transaction,?debugenabled,?suspendedresources);
}
catch?(runtimeexception?|?error?ex)?{
resume(null,?suspendedresources);
throw?ex;
}
}addgood()獲得事務并創(chuàng)建回滾點
addgood()從threadlocal中獲得addareaandgood()創(chuàng)建的事務，然后發(fā)現(xiàn)自己的傳播屬性為propagation_nested，就創(chuàng)建了一個回滾點。
org.springframework.transaction.support.abstractplatformtransactionmanager#handleexistingtransaction
if?(definition.getpropagationbehavior()?==?transactiondefinition.propagation_nested)?{
if?(!isnestedtransactionallowed())?{
throw?new?nestedtransactionnotsupportedexception(
"transaction?manager?does?not?allow?nested?transactions?by?default?-?"?+
"specify?'nestedtransactionallowed'?property?with?value?'true'");
}
if?(debugenabled)?{
logger.debug("creating?nested?transaction?with?name?["?+?definition.getname()?+?"]");
}
if?(usesavepointfornestedtransaction())?{
//?create?savepoint?within?existing?spring-managed?transaction,
//?through?the?savepointmanager?api?implemented?by?transactionstatus.
//?usually?uses?jdbc?3.0?savepoints.?never?activates?spring?synchronization.
defaulttransactionstatus?status?=
preparetransactionstatus(definition,?transaction,?false,?false,?debugenabled,?null);
//?創(chuàng)建回滾點
status.createandholdsavepoint();
return?status;
}
else?{
//?nested?transaction?through?nested?begin?and?commit/rollback?calls.
//?usually?only?for?jta:?spring?synchronization?might?get?activated?here
//?in?case?of?a?pre-existing?jta?transaction.
return?starttransaction(definition,?transaction,?debugenabled,?null);
}
}addgood()提交事務時釋放回滾點
addgood()并不會真正的提交事務，因為事務并不是addgood()創(chuàng)建的，只是在提交時會將之前創(chuàng)建的回滾點釋放。
org.springframework.transaction.support.abstractplatformtransactionmanager#processcommit
if?(status.hassavepoint())?{
//?nested的提交
if?(status.isdebug())?{
logger.debug("releasing?transaction?savepoint");
}
unexpectedrollback?=?status.isglobalrollbackonly();
//?只是釋放回滾點
status.releaseheldsavepoint();
}addarea()獲得事務并創(chuàng)建回滾點
流程與addgood()一致。
addarea()回滾事務釋放回滾點
addarea()發(fā)生異常，會執(zhí)行回滾事務的邏輯，并沒有真正的回滾事務，因為事務并不是addarea()創(chuàng)建的，，只是將之前創(chuàng)建的回滾點釋放。 org.springframework.transaction.support.abstractplatformtransactionmanager#processrollback
if?(status.hassavepoint())?{
//?用于nested傳播機制，發(fā)生異常
//?回滾至回滾點
if?(status.isdebug())?{
logger.debug("rolling?back?transaction?to?savepoint");
}
status.rollbacktoheldsavepoint();
}addareaandgood()回滾這個事務
addarea()發(fā)生異常后繼續(xù)往外拋，addareaandgood()也會捕獲到異常，然后執(zhí)行回滾邏輯，這樣整個事務都回滾了。 org.springframework.transaction.support.abstractplatformtransactionmanager#processrollback
else?if?(status.isnewtransaction())?{
//?只有最外層的事務newtransaction=true
if?(status.isdebug())?{
logger.debug("initiating?transaction?rollback");
}
//?事務的回滾
/**
?*?@see?org.springframework.jdbc.datasource.datasourcetransactionmanager#dorollback(org.springframework.transaction.support.defaulttransactionstatus)
?*/
dorollback(status);
}為什么將addarea()方法try catch起來，整個事務就不會回滾了呢？
因為將addarea()方法try catch起來后，addareaandgood()就會執(zhí)行提交事務的邏輯，這樣addgood()就被提交了。
關于 "spring的事務傳播屬性required_nested的原理介紹" 就介紹到此。希望多多支持碩編程。
Java技巧