案例引入
假如我们有下面这个config，其中必填的参数有很多，非必填的参数也有几个，maxThread和cpuCore 存在依赖关系。我们可以通过构造参数 + set 来进行赋值操作, 可以实现我们的功能。
java
public class VirtualHostConfig {
/**
* 构造函数
*/
public VirtualHostConfig(String host, int port, int cpuCore, int diskSize, int netWorkTraffic, int maxThread, boolean allowSsh) {
this.host = host;
this.port = port;
this.cpuCore = cpuCore;
this.diskSize = diskSize;
this.netWorkTraffic = netWorkTraffic;
this.allowSsh = allowSsh;
this.maxThread = maxThread;
if (StrUtil.isBlank(host)) {
System.out.println("host must fill");
throw new RuntimeException("host must fill");
}
if (this.port <= 0 || this.port >= 65535) {
System.out.println("port invalid");
throw new RuntimeException("port invalid");
}
if (this.cpuCore <= 0 || this.cpuCore > 8) {
System.out.println("cpu core must lt 8");
throw new RuntimeException("cpu core must lt 8");
}
if (this.maxThread <= 0 || this.maxThread > 8) {
System.out.println("maxThread must lt 8");
throw new RuntimeException("maxThread must lt 8");
}
if (this.diskSize < 256 || this.diskSize > 1024 || this.diskSize % 8 != 0) {
System.out.println("diskSize not valid");
throw new RuntimeException("diskSize not valid");
}
if (this.netWorkTraffic < 1 || this.netWorkTraffic > 10) {
System.out.println("netWorkTraffic invalid");
throw new RuntimeException("netWorkTraffic invalid");
}
// 存在依赖关系
if (this.maxThread > this.cpuCore) {
System.out.println("maxThread invalid");
throw new RuntimeException("maxThread invalid");
}
}
/**
* 必填 主机名称
*/
private String host;
/**
* 必填 0~65535
*/
private int port = -1;
/**
* 非必填 但是不能超过 cpuCore
*/
private int maxThread;
/**
* 必填 CPU 不超过8 填完不允许修改
*/
private int cpuCore = -1;
/**
* 非必填 缓存 不超过 512
*/
private int cacheSize = -1;
/**
* 非必填 服务器别名
*/
private String alisaName;
/**
* 必填 磁盘大小
*/
private int diskSize = -1;
/**
* 必填 网络带宽
*/
private int netWorkTraffic = -1;
/**
* 必填 是否允许ssh
*/
private boolean allowSsh;
public int getMaxThread() {
return maxThread;
}
public void setMaxThread(int maxThread) {
this.maxThread = maxThread;
}
public int getCacheSize() {
return cacheSize;
}
public void setCacheSize(int cacheSize) {
this.cacheSize = cacheSize;
}
public String getAlisaName() {
return alisaName;
}
public void setAlisaName(String alisaName) {
this.alisaName = alisaName;
}
public String getHost() {
return host;
}
public int getPort() {
return port;
}
public int getCpuCore() {
return cpuCore;
}
public int getDiskSize() {
return diskSize;
}
public int getNetWorkTraffic() {
return netWorkTraffic;
}
public boolean isAllowSsh() {
return allowSsh;
}
}现在有这样几个需求：
1 要求这个config一旦填好了以后不可以修改。
2 公司要求参数方法的参数列表不可超过5个，否则扣钱。
为了满足2这个时候我们可以也可以把必填的参数通过set的方式来注入，但是这样违背了1，同样之前非必填通过set注入也违背了1.并且如果通过set注入的话，我们的校验逻辑也没有地方放置。这个时候构造模式来拯救我们了。
构造者模式
java
public class VirtualHostConfig {
/**
* 必填 主机名称
*/
private String host;
/**
* 必填 0~65535
*/
private int port = -1;
/**
* 非必填 但是不能超过 cpuCore
*/
private int maxThread;
/**
* 必填 CPU 不超过8 填完不允许修改
*/
private int cpuCore = -1;
/**
* 非必填 缓存 不超过 512
*/
private int cacheSize = -1;
/**
* 非必填 服务器别名
*/
private String alisaName;
/**
* 必填 磁盘大小
*/
private int diskSize = -1;
/**
* 必填 网络带宽
*/
private int netWorkTraffic = -1;
/**
* 必填 是否允许ssh
*/
private boolean allowSsh;
public VirtualHostConfig(Builder builder) {
this.host = builder.host;
this.port = builder.port;
this.cpuCore = builder.cpuCore;
this.diskSize = builder.diskSize;
this.netWorkTraffic = builder.netWorkTraffic;
this.allowSsh = builder.allowSsh;
this.alisaName = builder.alisaName;
this.cacheSize = builder.cacheSize;
this.maxThread = builder.maxThread;
}
public int getMaxThread() {
return maxThread;
}
public void setMaxThread(int maxThread) {
this.maxThread = maxThread;
}
public int getCacheSize() {
return cacheSize;
}
public void setCacheSize(int cacheSize) {
this.cacheSize = cacheSize;
}
public String getAlisaName() {
return alisaName;
}
public void setAlisaName(String alisaName) {
this.alisaName = alisaName;
}
public String getHost() {
return host;
}
public int getPort() {
return port;
}
public int getCpuCore() {
return cpuCore;
}
public int getDiskSize() {
return diskSize;
}
public int getNetWorkTraffic() {
return netWorkTraffic;
}
public boolean isAllowSsh() {
return allowSsh;
}
static class Builder {
/**
* 必填 主机名称
*/
private String host;
/**
* 必填 0~65535
*/
private int port = -1;
/**
* 非必填 但是不能超过 cpuCore
*/
private int maxThread;
/**
* 必填 CPU 不超过8 填完不允许修改
*/
private int cpuCore = -1;
/**
* 非必填 缓存 不超过 512
*/
private int cacheSize = -1;
/**
* 非必填 服务器别名
*/
private String alisaName;
/**
* 必填 磁盘大小
*/
private int diskSize = -1;
/**
* 必填 网络带宽
*/
private int netWorkTraffic = -1;
/**
* 必填 是否允许ssh
*/
private boolean allowSsh;
public Builder() {
}
public Builder host(String host) {
this.host = host;
return this;
}
public Builder alisaName(String alisaName) {
this.alisaName = alisaName;
return this;
}
public Builder port(int port) {
this.port = port;
return this;
}
public Builder diskSize(int diskSize) {
this.diskSize = diskSize;
return this;
}
public Builder cacheSize(int cacheSize) {
this.cacheSize = cacheSize;
return this;
}
public Builder netWorkTraffic(int netWorkTraffic) {
this.netWorkTraffic = netWorkTraffic;
return this;
}
public Builder cpuCore(int cpuCore) {
this.cpuCore = cpuCore;
return this;
}
public Builder allowSsh(boolean allowSsh) {
this.allowSsh = allowSsh;
return this;
}
public Builder maxThread(int maxThread) {
this.maxThread = maxThread;
return this;
}
public VirtualHostConfig build() {
if (StrUtil.isBlank(host)) {
System.out.println("host must fill");
throw new RuntimeException("host must fill");
}
if (this.port <= 0 || this.port >= 65535) {
System.out.println("port invalid");
throw new RuntimeException("port invalid");
}
if (this.cpuCore <= 0 || this.cpuCore > 8) {
System.out.println("cpu core must lt 8");
throw new RuntimeException("cpu core must lt 8");
}
if (this.maxThread <= 0 || this.maxThread > 8) {
System.out.println("maxThread must lt 8");
throw new RuntimeException("maxThread must lt 8");
}
if (this.diskSize < 256 || this.diskSize > 1024 || this.diskSize % 8 != 0) {
System.out.println("diskSize not valid");
throw new RuntimeException("diskSize not valid");
}
if (this.netWorkTraffic < 1 || this.netWorkTraffic > 10) {
System.out.println("netWorkTraffic invalid");
throw new RuntimeException("netWorkTraffic invalid");
}
// 存在依赖关系
if (this.maxThread > this.cpuCore) {
System.out.println("maxThread invalid");
throw new RuntimeException("maxThread invalid");
}
return new VirtualHostConfig(this);
}
}
}是不是感觉这种写法更好呢？这样设置了属性以后就不可以被修改了。
java
public static void main(String[] args) {
VirtualHostConfig config = new Builder()
.host("127.0.0.1")
.cpuCore(8)
.netWorkTraffic(2)
.port(8989)
.diskSize(512)
.cacheSize(128)
.alisaName("server1")
.allowSsh(false)
.maxThread(7)
.build();
System.out.println(JSONUtil.toJsonStr(config));
}